Sticky cleaner

ABSTRACT

Provided is a sticky cleaner whose adhesive face can be easily renewed and whish is less susceptible to roll-loosening. The sticky cleaner provided by this invention comprises a PSA tape having an adhesive face on the first face of a substrate. The PSA tape forms a PSA tape roll wound with the adhesive face on the outside. On the first face of the substrate, the PSA tape comprises a first layer formed of a PSA and a second layer formed of an acrylic viscoelastic material. The adhesive face comprises first sections where the first layer is exposed and second sections where the second layer is exposed. The second sections protrude further out of the PSA tape roll relative to the first sections. The PSA tape roll shows an unwinding force F0 at 0° C. and an unwinding force F30 at 30° C.

This is a divisional of application Ser. No. 15/749,337, filed Jan. 31,2019, which is a National Stage of International Application No.PCT/JP2017/011434, filed on Mar. 22, 2017, which claims priority toJapanese Patent Application No. 2016-134455 filed on Jul. 6, 2016; theentire contents thereof are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a sticky cleaner.

BACKGROUND ART

As a means to clean floors, carpets, etc., a sticky cleaner(dirt-collecting device) using pressure-sensitive adhesive (PSA) tape iswidely used. In the sticky cleaner, the PSA tape is in an embodimentwhere it has an adhesive face on a strip of substrate and is wound in aroll with the adhesive face on the outside, forming a PSA tape roll; andthe adhesive face can be rolled over in contact with a surface to becleaned such as a floor surface to collect dust (substances to beremoved such as waste matters) on the surface to be cleaned. Technicaldocuments related to this type of art include Patent Documents 1 and 2.

CITATION LIST Patent Literature

[Patent Document 1] WO 2011/004662

[Patent Document 2] Japanese Patent Application Publication No.2009-219574

SUMMARY OF INVENTION Technical Problem

As for such a PSA tape roll, when the adhesive strength weakens upon alarge accumulation of dust on the roll surface (the outermostcircumferential adhesive face of the PSA tape), the outermostcircumferential part of the PSA tape can be withdrawn (unwound) from theroll and cut off to expose a new adhesive face on the roll surface. Inother words, it is constructed so that by the withdrawing and cuttingprocedure, the adhesive face exposed on the roll surface can be renewedto maintain desirable adhesive strength. In the procedure for renewingthe adhesive face, when the force required for withdrawal of the PSAtape from the roll (i.e. the unwinding force, or the force resistive tothe unwinding) is excessively large, the PSA tape is likely to tear orsplit against the will (at an unintended location) and the use of thePSA tape roll may be hindered. Especially, at a low temperature, suchtearing and splitting are more likely to occur since the unwinding forcetends to increase as compared to at room temperature. On the other hand,when the unwinding force is small, rolling the PSA tape roll over thetarget surface (a surface to be cleaned) is likely to cause so-calledrail drawing which is a situation where the adhesive strength betweenthe PSA tape and the target surface overcomes the unwinding force,causing adhesion of the PSA tape to the target surface accompanyingunrolling of the roll. In addition, when the unwinding force is small,loosening of the PSA tape roll (roll-loosening, i.e. lifting or openingof the winding end edge of the PSA tape from the outer surface of theinner circumferential of the roll) is likely to develop when not in use(during storage). The loosening of the PSA tape may not only degrade theappearance of the PSA tape roll, but also cause issues such asaccumulation of dust from the air onto the adhesive face causing adecrease in adhesive strength.

An objective of this invention is to provide a sticky cleaner whoseadhesive face can be easily renewed and which is less susceptible toroll-loosening.

Solution to Problem

This description provides a sticky cleaner that comprises a PSA tapehaving an adhesive face on a first face of a substrate. The PSA tapeconstitutes a PSA tape roll wound with the adhesive face on the outside.On the first face of the substrate, the PSA tape has a first layerformed of a PSA and a second layer formed of a viscoelastic material.The viscoelastic material forming the second layer is typically anacrylic viscoelastic material. The adhesive face comprises a firstsection where the first layer is exposed and a second section where thesecond layer is exposed. Relative to the first section, the secondsection protrudes further out of the PSA tape roll. The PSA tape rollexhibits an unwinding force F₀ at 0° C. and an unwinding force F₃₀ at30° C., F₀ being up to 10 times F₃₀. Such an embodiment can favorablyachieve both easy renewal of the adhesive face and inhibition ofroll-loosening.

Second sections are preferably formed separated by spaces in the widthdirection. According to such an embodiment, the plurality of secondsections are used as spacers to allow suitable control of the tightnessof adhesion between interleaving sections (e.g. first sections) and thesurface being cleaned or the backside of the PSA tape. Here, the“backside” of the PSA tape refers to the face opposite of the front faceof the PSA tape that comes in contact with an article, that is, the faceon the inside of the PSA tape roll.

In a preferable embodiment, the second sections are formed as linesrunning in the length direction of the PSA tape. As in this embodiment,when the second sections protruding further than the first sections areformed as lines running in the length direction (in the circumferentialdirection of the PSA tape roll), the procedures of withdrawing the PSAtape from the PSA tape roll and rolling the PSA tape roll over thetarget surface can be carried out smoothly.

In an embodiment of the sticky cleaner disclosed herein, the secondlayer has a cross-sectional area A (mm²) in the width direction of thePSA tape and a percent (%) weight R of the elastomer content in thesecond layer, having a product (an AR value) equal to or less than 2.5.Such an embodiment can facilitate hand-tearing of the PSA tape.

In a preferable embodiment, lines of the second layer are placed,running in the length direction of the PSA tape, separated by spaces inthe width direction of the PSA tape. Such an embodiment allows suitablecontrol of the tightness of adhesion to the surface being cleaned and tothe backside of the PSA tape. It also allows smooth withdrawal of thePSA tape from the PSA tape roll as well as smooth rotation of the PSAtape roll over the surface subject to cleaning.

As the acrylic viscoelastic material forming the second layer, aviscoelastic material comprising an acrylic block copolymer as the basepolymer can be preferably used. The art disclosed herein can befavorably implemented in an embodiment using such an acrylicviscoelastic material.

The second layer can comprise a filler. The art disclosed herein can befavorably implemented in an embodiment where the second layer has such acomposition.

In a preferable embodiment, the first layer is a rubber-based PSA layer.The art disclosed herein can be favorably implemented in an embodimentwhere the first layer is formed of a rubber-based PSA and the secondlayer is formed of an acrylic viscoelastic material.

In a preferable embodiment, the PSA tape roll has cut holes running in adirection intersecting the length direction, e.g. the width direction,of the PSA tape. Such cut holes are used to help separate part of thePSA tape from the rest so as to facilitate renewal of the adhesive faceof the PSA tape roll.

In an area up to one-fourth the circumference inward from the windingend edge of the PSA tape, the sticky cleaner disclosed herein may havean anti-rail-drawing portion where the adhesiveness of the PSA tape isreduced. With such a configuration, the anti-rail-drawing portion caneffectively prevent rail drawing, but the presence of theanti-rail-drawing portion is likely to cause loosening of the PSA tape.Thus, it is particularly meaningful to apply the present invention toinhibit loosening of the PSA tape.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a perspective diagram schematically illustrating the PSAtape roll of the sticky cleaner according to an embodiment.

FIG. 2 shows a cross-sectional diagram at line II-II in FIG. 1.

FIG. 3 shows a front view schematically illustrating the sticky cleaneraccording to an embodiment.

FIG. 4 shows a diagram viewed in the direction of arrow IV in FIG. 3.

FIG. 5 shows a cross-sectional diagram schematically illustrating thePSA tape forming the PSA tape roll in the sticky cleaner according toanother embodiment.

FIG. 6 shows a cross-sectional diagram schematically illustrating thesubstrate of the sticky cleaner shown in FIG. 5.

FIG. 7 shows a perspective diagram schematically illustrating the PSAtape roll of the sticky cleaner according to another embodiment.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention are described below.Matters necessary to practice this invention other than thosespecifically referred to in this description may be understood to aperson ordinarily skilled in the art based on the teachings aboutembodiments of the invention in this description and common technicalknowledge at the time the application was filed. The present inventioncan be implemented based on the contents disclosed herein and commontechnical knowledge in the subject field. In the following drawings,members and sites providing the same effect may be indicated by the samereference numeral, and redundant descriptions may be omitted orsimplified. The embodiments in the drawings are schematicallyillustrated for clearly describing the present invention, and do notnecessarily represent the dimensions or scales of an actual product.

Several embodiments of the sticky cleaner provided by the presentinvention are described with reference to drawings.

First Embodiment

FIG. 1 shows a perspective view of the PSA tape roll in the stickycleaner according to an embodiment. FIG. 2 shows its cross section atline II-II. PSA tape roll 10 is obtained from PSA tape 12 having anadhesive face 35 formed on the first face 20A of a tape (a long strip)of substrate 20, by winding PSA tape 12 around a core 14 in a roll withthe adhesive face 35 on the outside (on the outer circumference of theroll). From the standpoint of the cost, the ease of disposal, thecushioning properties, etc. as the core 14, a core made of paper(typically cardboard) can be preferably used. Alternatively, a core madeof other material (e.g. synthetic resin) can be used as well. The PSAtape roll can be of the so-called core-free type, obtainable by windingsolely PSA tape 12 in a roll without using core 14. That is, in thepresent invention, the core 14 is an optional constituent.

PSA tape 12 is provided with cut holes 24 for tearing at intervalsapproximately equal to the circumference of the roll. Cut holes 24provide a cutting means to facilitate cutting an end piece (a piece atone terminal of the length direction) of PSA tape 12 off the rest.Examples include a row of long holes or wavy slits, and intermittentslits such as a perforation. In the example shown in FIG. 1, cut holes24 are provided in the width direction (a direction perpendicularlyintersecting the length direction) of PSA tape 12, but can be provideddiagonally to the width direction. The direction in which the cut holesrun may stay the same or change somewhere in the middle. For instance,somewhere in the middle of the width of the PSA tape, there may be one,two or more points where the direction in which the cut holes runchanges in an angular or curved manner. In the example shown in FIG. 1,cut holes 24 are provided across the entire width of PSA tape 12.Alternatively, cut holes 24 can be provided from one end of the width ofPSA tape 12 up to a certain point in the middle so as to provide a startpoint of cutting.

PSA tape roll 10 in such an embodiment can be used along with, forinstance, a jig 50 as shown in FIG. 3, in a sticky cleaner 1 with PSAtape roll 10 being attached to a rolling member 52 of the jig 50.Rolling member 52 is bar-shaped and is supported on one end of a holdingbar 54 in a freely rotatable manner. Sticky cleaner 1 is configuredwhere rolling member 52 is inserted into core 14 of PSA tape roll 10 sothat PSA tape roll 10 and rolling member 52 rotate together in thecircumferential direction of the roll.

The form of the jig constituting the sticky cleaner is not limited tothe particular kind shown in FIG. 3. Various jigs can be used inaccordance with the purpose and application. The sticky cleaner providedby this description is not limited to an embodiment comprising a jig anda PSA tape roll as shown in FIG. 3. The PSA tape roll can be used as isas a sticky cleaner. That is, the PSA tape roll disclosed herein can bethought as a sticky cleaner as well. The concept of sticky cleanerprovided by this description encompasses a PSA tape roll used as asticky cleaner refill that is attached as necessary to a suitable jig inan exchangeable manner or for one time use.

In the following, the constitution of PSA tape 12 is described furtherin detail. PSA tape 12 has substrate 20, the first layer 31 formed onthe first face 20A thereof, and the second layer 32 formed partially onthe first layer 31. The first layer 31 is a layer formed of a PSA; inthe present embodiment, it is a rubber-based PSA layer formed of arubber-based PSA. The second layer 32 is a layer formed of aviscoelastic material, typically an acrylic viscoelastic layer formed ofan acrylic viscoelastic material. The adhesive face 35 showsadhesiveness as a whole with an alternating array of first sections 31Awhere the first layer 31 is exposed and second sections 32A where thesecond layer 32 is exposed. Here, relative to the first sections 31A,the second sections 32A protrude further out (to the outer circumferenceside) of PSA tape roll 10. With such a constitution, when PSA tape 12 iswound in a roll (i.e. in the embodiment of PSA tape roll 10), thesurface area where the first layer 31 directly adheres to the backside20B of PSA tape 12 can be reduced, thereby facilitating withdrawal(unwinding) of PSA tape 12 from PSA tape roll 10.

The adhesive face 35 may cover the entire first face 20A of substrate 20(i.e. at least either the first layer 31 or the second layer 32 ispresent in every part of the face), or may not be present in some areas.For instance, as shown in FIGS. 1 and 2, along the two edges of thewidth direction (the two lengthwise edges) of substrate 20, there may benon-adhesive areas (dry edges) 22 and 23 where the adhesive face 35 isnot formed. Each of the non-adhesive areas 22 and 23 can have a widthof, for instance, about 1 mm to 20 mm (typically 3 mm to 15 mm). Thewidths of the non-adhesive areas 22 and 23 can be the same or different.Alternatively, only one of the lengthwise edges may be provided with anon-adhesive area. With respect to the entire length of substrate 20,the non-adhesive area can be provided only partially in a continuous orintermittent manner.

In this embodiment, the first layer 31 is formed (spread) evenly andcontinuously in the entire area of substrate 20 or in some areas leavingout the non-adhesive areas. The thickness (T1 in FIG. 2) of the firstlayer 31 can be suitably selected to obtain desirable adhesiveproperties in accordance with the application of PSA tape roll 10. Thethickness T1 of the first layer 31 is usually suitably 2 μm or greater,5 μm or greater, or even 10 μm or greater. A large thickness T1 of thefirst layer 31 tends to enhance the cleaning ability (typically theability to collect dust on the surface being cleaned). On the otherhand, from the standpoint of making a smaller, lighter PSA tape roll 10and saving resources, the thickness T1 of the first layer 31 is usuallysuitably about 50 μm or less, preferably about 35 μm or less, or evenabout 25 μm or less (e.g. about 20 μm or less). The surface of thecontinuously-formed first layer 31 may be smooth or may have microcontours (e.g. hairline texture). The micro contours on the surface ofthe first layer 31 can enhance the dust-collecting ability.

The planar shape, cross-sectional shape and arrangement of the secondlayer 32 can be selected to suitably reduce the area where the firstlayer 31 adheres directly to the second face (backside) 20B of PSA tape12. For instance, in a preferable embodiment, several lines of thesecond layer 32 are arranged almost in parallel to one another. Theplanar shape of each line of the second layer 32 can be linear(straight), curvilinear, polygonal, wavy, etc. From the standpoint ofthe ease of manufacturing, the second layer 32 is preferably formed instraight lines. In this embodiment, on the first layer 31, straightlines of the second layer 32 running in the length direction of PSA tape12 are arranged almost in parallel to one another (in a stripe pattern),separated by spaces in the width direction of the PSA tape 12. PSA taperoll 10 in such an embodiment is preferable because the structure(cross-sectional shape) of PSA tape 12 stays constant in cross sectionslined in the length direction, with little fluctuation both in force ofunwinding the tape in the length direction and in operational feeling(response from the resistance to operation) in relation to rolling ofPSA tape roll 10 on the surface being cleaned (target surface). That is,the unwinding and the rolling can be carried out more smoothly. This canbe advantageous from the standpoint of reducing rolling noise associatedwith its rotation on a hard, smooth surface such as a wood flooringsurface, etc.

The PSA tape roll disclosed herein may be in an embodiment having afirst group consisting of straight lines of the second layer runningalmost in parallel to one another in a first direction and a secondgroup consisting of straight lines of the second layer running almost inparallel to one another in a direction intersecting (in typical,perpendicularly) the first direction. For instance, in an embodiment,the first group of lines of the second layer and the second group oflines of the second layer may be arrayed in a lattice pattern.

When the second layer 32 is formed in lines, the width (W2 in FIG. 2) ofeach line is not particularly limited and can be designed in accordancewith the application (e.g. the material and the state of the surface tobe cleaned, matters to be removed, etc.; the same applies hereinafter)as well as with the constitution of the first layer 31, dimensions ofPSA tape roll 10, etc. In an embodiment, the line width W2 of the secondlayer 32 can be, for instance, about 0.1 mm or greater, about 0.15 mm orgreater, about 0.2 mm or greater, or even about 0.3 mm or greater. W2can be, for instance, about 5 mm or less, about 2 mm or less, about 1 mmor less, about 0.7 mm or less, or even about 0.5 mm or less. Byadjusting W2, the unwinding force and the operational feeling during usecan be adjusted. When the line width of the second layer 32 changes fromplace to place (e.g. the lines run while their width repeatedlyfluctuates up and down in a gradual or stepwise manner), theaforementioned ranges of W2 values can be applied to the average linewidth of the second layer 32 over a certain length.

Preferably, the lines of the second layer 32 are arranged almost evenlyover the entire adhesive face 35. For instance, in an embodiment asshown in FIGS. 1 and 2 where the lines of the second layer 32 arearranged almost in parallel to one another, the line pitch (P in FIG. 2)of the second layer 32 is preferably almost constant. The pitch P is notparticularly limited and can be designed in accordance with theapplication, the constitution of the first layer 31, dimensions of PSAtape roll 10, etc. In an embodiment, the pitch P of the second layer 32can be, for instance, about 0.5 mm or greater, usually suitably about 1mm or greater, or possibly 1.5 mm or greater. The pitch P of the secondlayer 32 can be, for instance, about 10 mm or less, usually suitablyabout 5 mm or less, possibly about 4 mm or less, or even 3 mm or less.

In another embodiment of the PSA tape roll disclosed herein, the secondlayer can be formed in dots (spots or islets) arranged in a certainpattern or in a random manner. The shapes of the second layer dots arenot particularly limited. Examples include circles, ovals, ellipsoids,circular sectors (e.g. semicircles), rings, quadrilaterals (squares,rectangles, trapezoids, rhombi, etc.), non-quadrilateral polygons(triangles, hexagons, etc.) as well as shapes representing variousdesigns, symbols and letters. When the second layer 32 is formed indots, each dot can have a surface area of, for instance, about 0.1 mm²or greater, or usually suitably about 0.5 mm² or greater (e.g. about 1mm² or greater). The surface area of each dot can be, for instance,about 25 mm² or less, usually suitably about 10 mm² or less (e.g. about5 mm² or less). Two adjacent dots of the second layer can be spacedapart by, for instance, about 0.1 mm to 10 mm (typically about 0.5 mm to5 mm, e.g. about 1 mm to 3 mm).

Part of the adhesive face 35 is formed with the second sections 32Awhere the second layer 32 is exposed. The second sections 32A protrudefurther out, at least partially, relative to the first sections 31A. Insuch an embodiment, for instance, when the adhesive face 35 is rotatedon a hard, smooth surface (a wood flooring surface, etc.) to clean thesurface, the second sections 32A are more likely to come in contact withthe target surface while the first sections 31A make limited contactwith the target surface. This can prevent the resistance to operation tobe excessively high during use and can also avoid rail drawing. On theother hand, when a flexible rough surface (a carpet surface, etc.) iscleaned, deformation of the target surface increases the area of contactbetween the first sections 31A and the target surface, giving rise to agood dust-collecting ability. Thus, the sticky cleaner in the presentembodiment can be preferably used on surfaces of various materials andproperties.

In this embodiment, the thickness T2 of the second layer is theprotruding height of the second sections 32A relative to the firstsections 31A. While no particular limitations are imposed, theprotruding height T2 can be, for instance, about 10 μm or greater, about20 μm or greater, about 30 μm or greater, or even about 40 μm orgreater. A larger protruding height T2 brings about a greater effect torestrict contact between the first sections 31A and the target surface.The protruding elastic second layer 32 provides adequate cushioningproperties to PSA tape roll 10 to reduce the rolling noise during itsuse. With the cushioning properties, the area of contact between theadhesive face 35 (especially the first sections 31A) and the targetsurface can be adjusted easily by the pressure onto the target surface.In an embodiment, the protruding height T2 can be about 50 μm or greater(e.g. about 60 μm or greater). The protruding height T2 can be, forinstance, about 2 mm or less (typically about 1 mm or less). From thestandpoint of the ease of forming the second layer 32 and the retentionof the shape, it is usually suitably about 500 μm or less, or preferablyabout 150 μm. The protruding height T2 can be about 100 μm or less, oreven about 85 μm or less. With decreasing protruding height T2, thethickness of the second layer 32 generally decreases as well. This canbe advantageous from the standpoint of reducing formation of stickystrings (cobwebbing) of the second layer 32 while PSA tape 12 is tornoff. The art disclosed herein can be favorably implemented in anembodiment where the protruding height T2 is, for instance, about 65 μmor less (or even about 50 μm or less).

In an embodiment, the protruding height T2 of the second sections 32Acan be greater than the thickness T1 of the first layer 31 (i.e. T1<T2).According to such an embodiment, a PSA tape roll having favorablecushioning properties is likely to be obtained. The art disclosed hereincan be preferably implemented in an embodiment where the protrudingheight T2 is about at least 1.5 times (typically at least 2 times, e.g.at least three times) the thickness T1. In a preferable embodiment, theprotruding height T2 is up to about 10 times (typically up to 7 times,e.g. up to 5 times) the thickness T1.

The percent surface area of the second sections 32A in the combinedsurface area of the first and second sections 31A and 32A can be, forinstance, 2% or higher, usually suitably 5% or higher, 10% or higher,15% or higher, or even 20% or higher. The percentage can be, forinstance, 70% or lower, usually suitably 50% or lower, 40% or lower, oreven 30% or lower. By adjusting the percent surface area between thefirst and second sections 31A and 32A, the operational feeling duringuse can be adjusted to a favorable range. With respect to the PSA taperoll 10 in the present embodiment, the combined surface area is equal tothe surface area of the adhesive face 35, and equal to the surface areaof where the first layer 31 is formed as well.

While no particular limitations are imposed, the height H from the firstface 20A of substrate 20 to the second sections 32A (corresponding tothe combined thickness of the first and second layers 31 and 32, i.e.T1+T2 in the present embodiment) can be, for instance, 250 μm or less,usually suitably 150 μm or less, or preferably 120 μm or less (e.g. 100μm or less). A small height H can be advantageous from the standpoint ofmaking the PSA tape roll smaller or increasing the length of the PSAtape constituting the roll. From the standpoint of the adhesiveproperties such as the ease of adjusting the unwinding force ratio, theheight H is usually suitably 15 μm or greater, preferably 25 μm orgreater, or more preferably 35 μm or greater (e.g. 45 μm or greater).

<Unwinding Force>

The PSA tape roll disclosed herein is constituted typically so that theunwinding force F₀ at 0° C. is up to 10 times the unwinding force F₃₀ at30° C. That is, the unwinding force ratio determined by F₀/F₃₀ (orsimply the unwinding force ratio, hereinafter) is 10 or lower. Theunwinding force ratio limited at or below the prescribed value meansthat the temperature dependence of the unwinding force is reduced. Thiscan favorably bring about a PSA tape roll which allows easy renewal ofthe adhesive face even at a low temperature while loosening of the rollis inhibited even at room temperature.

Here, the unwinding force of the PSA tape roll is determined as follows:

[Determination of Unwinding Force]

The PSA tape roll (specimen) to be measured is set in a tensile tester.At a measurement temperature of X ° C., the PSA tape roll end is clampedin the chuck of the tensile tester and pulled at a rate (unwindingspeed) of 1000 mm/min to unwind the PSA tape roll in the tangentialdirection. The tensile strength observed during this is converted asnecessary to the value per width of the adhesive face to determine theunwinding force F_(X) at X ° C. For instance, the tensile strength canbe converted to the value per 150 mm width of the adhesive face todetermine the unwinding force F_(X) in N/150 mm. When the adhesive faceof the specimen has a width of 150 mm, the measurement value can be usedas is (without conversion) as the unwinding force F_(X) in N/150 mm. Thesame method is used in the working examples described later. Atmeasurement temperatures of 0° C. and 30° C., unwinding forces F₀ andF₃₀ can be determined, respectively. The unwinding forces are desirablydetermined after PSA tape rolls to be measured are stored at themeasurement temperatures for at least one hour to equilibrate to thetemperatures.

In general, when the measurement environment is at a low temperature,the unwinding force of a PSA tape roll tends to increase. Thus, if theunwinding force is increased in order to inhibit rail drawing androll-loosening at room temperature (typically about 20° C. to 30° C.),the unwinding force will be excessively high for renewing the adhesiveface at a low temperature, making withdrawal of the PSA tape harder andleading to issues such as tearing and splitting of the PSA tape and poorefficiency due to attentions required for the withdrawal. On the otherhand, if the unwinding force is adjusted to facilitate the renewal ofthe adhesive face at a low temperature, rail drawing and roll-looseningare likely to occur at room temperature. According to the art disclosedherein, by lowering the unwinding force ratio, that is, by making theunwinding force less dependent on the temperature, efficient renewal ofthe adhesive face can be combined with prevention of rail drawing androll-loosening.

In the art disclosed herein, the unwinding force ratio of the PSA taperoll (i.e. F₀/F₃₀) is preferably about 8 or lower, more preferably about6 or lower, or even about 4 or lower (e.g. about 3 or lower). When theunwinding force ratio decreases (i.e. when the unwinding force becomesless dependent on the temperature), efficient renewal of the adhesiveface and prevention of rail drawing and roll-loosening can be combinedat a high level. The unwinding force ratio is usually about 1 or higher.When it is far below 1, issues such as anchoring failure may arise inmeasurement at a low temperature. With respect to the PSA tape rolldisclosed herein, better results tend to be obtained as the unwindingforce ratio approaches 1, but not below 1. On the other hand, from apractical viewpoint, the PSA tape roll disclosed herein can also befavorably made in an embodiment where the unwinding force ratio ishigher than 1 (e.g. about 1.2 or higher, or even about 1.5 or higher).The unwinding force ratio can be adjusted by selection of the materialforming the adhesive face, the structure of the adhesive face (e.g. thethicknesses of the first and second layers; shapes, dimensions andarrangement of the first and second sections; etc.), selection of thematerial forming the backside of the PSA tape, etc.

The unwinding force F₃₀ of the PSA tape roll at 30° C. is notparticularly limited. In an embodiment, when the unwinding force F₃₀ isabout 0.3 N/150 mm or greater, roll-loosening can be significantlyinhibited. When the unwinding force F₃₀ is about 0.5 N/150 mm or higher(e.g. about 0.7 N/150 mm or higher), greater effects can be obtained. Onthe other hand, from the standpoint of the ease of intentionallywithdrawing the PSA tape from the PSA tape roll for renewing theadhesive face, etc., and of preventing the adhesive face-formingmaterial from transferring (moving and sticking) to the backside of thePSA tape, the unwinding force F₃₀ is usually suitably about 5 N/150 mmor less (typically about 3 N/150 mm or less, e.g. about 2 N/150 mm orless), or even about 1.5 N/150 mm or less (e.g. about 1.0 N/150 mm orless).

The unwinding force F₀ of the PSA tape roll at 0° C. is not particularlylimited. It is usually suitably about 7 N/150 mm or less, preferablyabout 6.0 N/150 mm or less, more preferably about 5.0 N/150 mm or less,or possible about 4.0 N/150 mm or less (e.g. about 3.0 N/150 mm orless). A small unwinding force F₀ tends to facilitate withdrawal of thePSA tape from the PSA tape roll even at a low temperature. On the otherhand, from the standpoint of inhibiting rail drawing and roll-loosening,the unwinding force F₀ is usually suitably about 0.5 N/150 mm orgreater, or preferably about 1 N/150 mm or greater (e.g. about 1.5 N/150mm or greater). The respective unwinding forces at 0° C. and 30° C. canbe adjusted by selection of the material forming the adhesive face, thestructure of the adhesive face, selection of the material forming thebackside of the PSA tape, etc.

<Substrate>

As the substrate of the PSA tape roll, various types of resin film,paper, fabric, rubber sheet, foam sheet, metal foil, a composite ofthese and the like can be used. Examples of the resin film materialinclude polyolefins (polyethylene (PE), polypropylene (PP),ethylene-propylene copolymer, etc.), polyesters (polyethyleneterephthalate (PET), etc.), vinyl chloride resin, vinyl acetate resin,polyimide resin, polyamide resin, fluororesin, thermoplastic elastomer(TPE) (e.g. an olefinic thermoplastic elastomer) and acrylic resin. Asthe acrylic resin, either one can be used between a species synthesizedusing an acryloyl group-containing monomer in a larger amount (typicallyin a larger amount (by weight) than a methacryloyl group-containingmonomer) and a species synthesized using a methacryloyl group-containingmonomer in a larger amount (typically in a larger amount (by weight)than an acryloyl group-containing monomer). The concept of acrylic resinhere may encompass species generally called acrylic rubber. Examples ofpaper include Japanese paper (washi), kraft paper, glassine paper,high-grade paper, synthetic paper, and top-coated paper. Examples offabric include woven fabric and non-woven fabric of a single species ora blend of various fibrous substances. Examples of fibrous substancesinclude cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber,polyester fiber, polyvinyl alcohol fiber, polyamide fiber, andpolyolefin fiber. Examples of rubber sheets include natural rubbersheet, and butyl rubber sheet. Examples of foam sheets include resinfoam sheets such as polyolefin foam sheet (PE foam sheet, PP foam sheet,etc.), polyurethane foam sheet, and polychloroprene rubber foam sheet.Examples of metal foil include aluminum foil and copper foil. As usedherein, the resin film typically refers to non-porous film; it isdifferent from a foam sheet and is also conceptually distinguished fromso-called non-woven fabric and woven fabric. To the material mixtureforming the substrate, as necessary various additives may be added, suchas filler (inorganic filler, organic filler, etc.), anti-aging agent,antioxidant, UV ray absorber, photostabilizer, anti-static agent,lubricant, plasticizer, colorant (pigment, dye, etc.).

The substrate may have a monolayer structure or a multilayer structurein which two or more layers are laminated. Preferable examples include apaper substrate having a release layer formed with a release agent onthe backside, a paper substrate laminated with resin film on thebackside, a paper substrate coated on the backside with a resin materialby hot melt extrusion, a monolayer or multilayer resin film, and amonolayer or multilayer resin foam sheet. In an embodiment, a substrateof which at least the second face is formed from a resin material(preferably a polyolefin resin, e.g. PE resin) can be used.

The first face (the face supporting the first and second layers whilefacing the outside of the PSA tape roll) may be subjected to a surfacetreatment to enhance anchoring to the first face, such as coronadischarge treatment and primer coating. Alternatively, a substrate whosefirst face has not been subjected to a surface treatment can be used aswell. With a substrate whose first face is made of paper or fabric, goodanchoring is likely to be obtained without requiring the surfacetreatment. This can be advantageous in view of reducing the cost,increasing the productivity, etc.

The substrate's second face (the face opposing the adhesive face whilefacing the inside of the PSA tape roll) may be subjected to a surfacetreatment such as coating of a release agent so as to adjust theunwinding force of the PSA tape roll to a suitable range. In apreferable embodiment, a paper substrate whose second face (possibly aface treated with known sealer) has been treated with a release agent, apaper substrate whose second face is laminated with resin film andtreated with a release agent, and the like can be used. The releaseagent used in the release treatment is not particularly limited. Forinstance, a silicone-based release agent, fluorine-based release agent,a long-chain alkyl-based release agent, and other known or commonly-usedrelease agents can be used in accordance with the purpose andapplication. For the release agent, solely one species or a combinationof two or more species can be used. In another preferable embodiment, asubstrate whose second face has not been subjected to the surfacetreatment can be used. For instance, by using a substrate whose secondface is formed from a low-polar resin material (e.g. a polyolefin resinsuch as PE resin) and suitably selecting the viscoelastic materialforming the second layer, a PSA tape roll that exhibits a suitableunwinding force without requiring the surface treatment (releasetreatment, etc.) can be favorably obtained.

In this embodiment, as shown in FIG. 2, a substrate 20 is used, having amultilayer structure in which a support layer 202 and a backside layer204 are laminated. Support layer 202 is made of paper (high-grade paperhere) and laminated with PE resin film on its second face side, with thePE resin film forming the backside layer 204. The second face 20B (thesurface of the backside layer 204) of substrate 20 is not treated with arelease agent.

In the art disclosed herein, the thickness of the substrate can besuitably selected in accordance with the purpose, and is notparticularly limited. In an embodiment, the thickness of the substratecan be, for instance, 200 μm or less, 150 μm or less, or even 100 μm orless (e.g. 80 μm or less). A smaller thickness of the substrate can beadvantageous from the standpoint of inhibiting roll-loosening. Thethickness of the substrate can be, for instance, 10 μm or greater,typically 25 μm or greater, preferably 40 μm or greater, or even 50 μmor greater. With increasing thickness of the substrate, the strength ofthe substrate tends to generally increase. Thus, a larger thickness ofthe substrate can be advantageous from the standpoint of preventingtearing and splitting while the PSA tape is withdrawn from the roll. Forinstance, such a thickness can be preferable for substrates made ofresin film, non-woven fabric and paper. For instance, in an embodimentusing a monolayer or multilayer substrate that includes a foam sheet,the thickness of the substrate is usually suitably 150 μm or greater(typically 300 μm or greater, preferably 500 μm or greater, e.g. 700 μmor greater); it is suitably 3 mm or less (typically 2 mm or less,preferably 1.5 mm or less, e.g. 1.2 mm or less).

The width of the substrate (the width of the PSA tape) can be suitablyselected in accordance with the purpose, and is not particularlylimited. From the standpoint of the ease of using the PSA tape roll, thewidth of the substrate is usually suitably 1 cm or greater, preferably 3cm or greater, 5 cm or greater, or even 10 cm or greater. A larger widthof the substrate tents to hinder withdrawal of PSA tape from the PSAtape roll and tends to cause roll-loosening as well. Accordingly, it issignificant to apply the art disclosed herein to facilitate theunwinding operation while inhibiting roll-loosening. From such astandpoint, the art disclosed herein can be preferably implemented in anembodiment where the substrate has a width of, for instance, about 12 cmor greater (typically about 14 cm or greater). The width of thesubstrate can be, for instance, about 100 cm or less, typically about 70cm or less, preferably about 50 cm or less, about 40 cm or less, about35 cm or less, or even about 30 cm or less (e.g. about 25 cm or less).The art disclosed herein can be preferably implemented in an embodimentwhere the substrate has a width of, for instance, about 10 cm or greaterand about 50 cm or less (preferably about 14 cm or greater and about 40cm or less).

The width of the adhesive face formed on the first face of the substrateis usually suitably about 0.8 cm or greater, preferably about 2.5 cm orgreater, about 4.5 cm or greater, or even about 9.5 cm or greater. Withincreasing width of the adhesive face, tearing and splitting tend to belikely to occur when withdrawing the PSA tape from the PSA tape roll.Accordingly, it is significant to apply the art disclosed herein tofacilitate unwinding and inhibit roll-loosening at the same time. Fromsuch a standpoint, the art disclosed herein can be preferablyimplemented in an embodiment where the adhesive face has a width of, forinstance, about 11 cm or greater (typically about 13 cm or greater). Thewidth of the adhesive face can be, for instance, about 98 cm or less,typically 68 cm or less, preferably about 48 cm or less, about 39 cm orless, about 34.5 cm or less, or even about 29.5 cm or less (e.g. about24.5 cm or less). The art disclosed herein can be preferably implementedin an embodiment where the adhesive face has a width of, for instance,about 9.5 cm or greater and about 48 cm or less (preferably about 13 cmor greater and 39 cm or less).

While no particular limitations are imposed, the cylindrical PSA taperoll may have a diameter of usually about 10 mm or greater (typically 30mm or greater, e.g. 40 mm or greater). Here, the diameter of the PSAtape roll refers to the diameter (outer diameter) of the unused PSA taperoll. The diameter of the PSA tape roll is usually about 200 mm or less(typically about 150 mm or less, preferably about 100 mm or less), oreven about 80 mm or less. The PSA tape forming the cylindrical PSA taperoll may have an inner diameter of usually about 8 mm or greater(typically 25 mm or greater, e.g. 35 mm or greater). Here, the innerdiameter of the PSA tape refers to the winding diameter of the PSA tapeat the beginning of its winding; in a PSA tape roll with the PSA tapewound on a core, it is generally equal to the outer diameter of thecore. The inner diameter of the PSA tape is usually about 190 mm or less(typically about 140 mm or less, preferably about 95 mm or less), or itcan also be about 75 mm or less. In the PSA tape roll, the thickness ofwound layers of the PSA tape (typically equivalent to one half thedifference between the diameter of the PSA tape roll and the innerdiameter of the PSA tape) is typically 1 mm or greater, preferably about2.5 mm or greater, or more preferably about 5 mm or greater (e.g. about7 mm or greater). From the standpoint of reducing the difference inoperational feeling of the PSA tape roll between start to end of itsuse, the thickness of wound layers is usually suitably about 50 mm orless, preferably about 30 mm or less, more preferably about 20 mm orless, or possibly about 15 mm or less (e.g. about 12 mm or less). Thewidth of the cylindrical PSA tape roll (the length in the direction ofthe winding axis) is normally about the same as the width of thesubstrate. The art disclosed herein can be preferably made in thesedimensions.

<First Layer>

Examples of the PSA forming the first layer include acrylic PSA,rubber-based PSA, polyester-based PSA, urethane-based PSA,polyether-based PSA and silicone-based PSA. Here, the rubber-based PSArefers to a PSA that comprises a rubber-based polymer as its basepolymer. The same applies to the other PSAs.

As used herein, the base polymer refers to the primary component (acomponent with the highest percentage) among polymers. In the polymercontent of the PSA disclosed herein, the base polymer content istypically about 50% by weight or higher, usually suitably about 70% byweight or higher, or even about 90% by weight or higher based onnon-volatiles. The base polymer content is 100% by weight at maximum.For instance, it can be about 99% by weight or lower. From thestandpoint of the adhesive properties and the cost, a rubber-based PSAor an acrylic PSA can be preferably used.

As the acrylic PSA, a PSA comprising an acrylic polymer as the basepolymer is used. Here, the acrylic polymer refers to a polymer whoseprimary monomer (the primary component among monomers forming theacrylic polymer, i.e. a component accounting for 50% by weight or moreof the total monomer content) is a monomer having at least one(meth)acryloyl group per molecule (which may be referred to as anacrylic monomer, hereinafter). The acrylic monomer may account for 70%or more (e.g. 90% or more) by weight of the monomers forming the acrylicpolymer. As used herein, the (meth)acryloyl group comprehensively refersto acryloyl group and methacryloyl group. Similarly, the (meth)acrylatehere comprehensively refers to acrylate and methacrylate.

Examples of the rubber-based PSA include a PSA that comprises, as thebase polymer, one, two or more species among rubber-based polymers suchas natural rubber-based polymers including natural rubber and modifiedproducts thereof, isoprene rubber, chloroprene rubber,styrene-isoprene-styrene block copolymer (SIS),styrene-butadiene-styrene block copolymer (SBS),styrene-ethylene/butylene-styrene block copolymer (SEBS), crystallinepolyolefin-ethylene/butylene-crystalline polyolefin block copolymer(CEBC), and styrene-ethylene/butylene-crystalline polyolefin blockcopolymer (SEBC).

A favorable example of the rubber-based PSA is a PSA (SIS-based PSA)comprising SIS as the base polymer. In this embodiment, the first layer31 is formed of an SIS-based PSA. In addition to the SIS as the basepolymer, the SIS-based PSA may comprise, for instance, a tackifier resin(tackifier) and process oil as major components. The respective speciesof components and their ratio can be selected in accordance with theapplication of the PSA tape roll so as to obtain desirable adhesiveproperties.

As the tackifier resin, solely one species or a suitable combination oftwo or more species can be used among various species of tackifier resinsuch as general rosin-based, terpene-based, hydrocarbon-based,epoxy-based, polyamide-based, elastomer-based, phenol-based, andketone-based species. While no particular limitations are imposed, theamount of the tackifier resin used to 100 parts by weight of the basepolymer can be, for instance, about 50 parts to 200 parts by weight; itis usually suitably about 80 parts to 150 parts by weight.

As the process oil, for instance, solely one species or a suitablecombination of two or more species can be used such as generalparaffin-based, naphthenic and aromatic process oils. While noparticular limitations are imposed, the amount of the process oil usedto 100 parts by weight of the base polymer can be, for instance, about50 parts to 200 parts by weight; it is usually suitably about 90 partsto 150 parts by weight.

To the PSA (e.g. an SIS-based PSA) forming the first layer, variousadditives can be further added, such as anti-aging agent, antioxidant,UV absorber, photostabilizer, antistatic agent, lubricant, and colorant(pigment, dye, etc.). The species of additives and their amounts addedcan be the same as for typical species and amounts added in the field ofgeneral PSA.

The PSA forming the first layer can be various types of PSA such as ahot melt type with which adhesive components are heated and melted toform a PSA layer, a water dispersion type (typically an emulsion type)in which adhesive components are dispersed in water, and a solvent typein which adhesive components are dissolved in an organic solvent. Fromthe standpoint of the productivity and reduction of environmentalburden, a hot melt PSA can be preferably used.

<Second Layer>

In this embodiment, as the viscoelastic material forming the secondlayer, an acrylic viscoelastic material can be used. The acrylicviscoelastic material refers to a viscoelastic material that comprisesan acrylic polymer as the base polymer, that is, a viscoelastic materialin which an acrylic polymer is the component with the highest percentageamong the polymers therein. Of the polymer content in the viscoelasticmaterial disclosed herein, the base polymer content (based onnon-volatiles) is typically about 50% by weight or higher, usuallysuitably about 70% by weight or higher, or possibly about 90% by weightor higher. The base polymer content is 100% by weight at maximum. Forinstance, it can be about 99% by weight or lower.

In the art disclosed herein, the viscoelastic material forming thesecond layer can be a material that exhibits pressure-sensitiveadhesiveness at room temperature (e.g. around 25° C.) (i.e. a PSA) orcan be a material that does not substantially exhibit pressure-sensitiveadhesiveness (i.e. a non-PSA). The composition of the firstlayer-forming PSA (first PSA) and the composition of the secondlayer-forming viscoelastic material can be the same or different. In anembodiment of the art disclosed herein, as the viscoelastic materialforming the second layer, a viscoelastic material (possibly a PSA)having a composition different from that of the first PSA can bepreferably used. The viscoelastic material forming the second layer mayhave, for instance, a composition obtained by adding an additionalcomponent (e.g. a filler) to the first PSA, or a composition obtained byincreasing or decreasing the amounts of some components (e.g. tackifier)in the first PSA. Alternatively, the base polymer species of the firstPSA can be a different species (e.g. a rubber-based polymer) from thebase polymer of the viscoelastic material forming the second layer. In apreferable embodiment, the viscoelastic material forming the secondlayer may be an acrylic PSA that is less adhesive as compared to thefirst PSA, or may be an acrylic non-PSA viscoelastic material.

With respect to the acrylic polymer as the base polymer of the acrylicviscoelastic material (preferably an acrylic PSA), when the monomersforming the polymer comprises two or more species of monomer, theacrylic polymer can be a random copolymer, a block copolymer, a graftcopolymer, etc. From the standpoint of the ease of production and thehandling properties, preferable acrylic polymers include a randomcopolymer and a block copolymer. For the acrylic polymer, solely onespecies or a combination of two or more species can be used.

(Acrylic Random Copolymer)

Examples of preferable acrylic polymer include an acrylic randomcopolymer derived from a starting monomer mixture that comprises analkyl (meth)acrylate having an alkyl group as the primary monomer. Asthe alkyl (meth)acrylate, for instance, a compound represented by ageneral formula (1) shown below can be preferably used:

CH₂═CR¹COOR²  (1)

Here, R¹ in the general formula (1) is a hydrogen atom or a methylgroup. R² is an acyclic alkyl group having 1 to 20 carbon atoms(hereinafter, such a range of the number of carbon atoms may beindicated as “C₁₋₂₀”). From the standpoint of the storage elasticmodulus of the acrylic viscoelastic material, etc., an alkyl(meth)acrylate with R² being a C₁₋₁₂ (e.g. C₂₋₁₀, typically C₄₋₈)acyclic alkyl group is preferable. These alkyl (meth)acrylates can beused singly as one species or in a combination of two or more species.Preferable alkyl (meth)acrylates include n-butyl (meth)acrylate,2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isononyl(meth)acrylate, and lauryl (meth)acrylate. It is particularly preferableto use either one or each of n-butyl acrylate (BA) and 2-ethylhexylacrylate (2EHA).

The ratio of the primary monomer in all the monomers forming the acrylicrandom copolymer is preferably about 60% by weight or higher, morepreferably about 80% by weight or higher, or yet more preferably about90% by weight or higher. The maximum ratio of the primary monomer in allthe monomers is not particularly limited. From the standpoint of easyadjustment of the properties (adhesive strength, cohesive strength,etc.) of the acrylic viscoelastic material, it is usually preferablyabout 99% by weight or less (e.g. about 98% by weight or less, typicallyabout 95% by weight or less). The acrylic random copolymer can be apolymerization product of the starting monomer mixture comprisingessentially of the primary monomer.

For adjusting the properties of the acrylic viscoelastic material, etc.,the starting monomer mixture used in polymerization of the acrylicrandom copolymer may further comprise, in addition to the primarymonomer, a secondary monomer copolymerizable with the primary monomer. Afavorable example of such a secondary monomer is a monomer having afunctional group (or a “functional group-containing monomer”hereinafter). The functional group-containing monomer can be added toincorporate crosslinking points into the acrylic polymer to facilitateadjustment of the properties (adhesive strength, cohesive strength,etc.) of the acrylic viscoelastic material. Examples of the functionalgroup-containing monomer include a carboxy-group-containing monomer, anacid-anhydride-group-containing monomer, a hydroxy-group-containingmonomer, an amide-group-containing monomer, an amino-group-containingmonomer, an epoxy-group (glycidyl group)-containing monomers, analkoxy-group-containing monomer, and an alkoxysilyl-group-containingmonomer. These can be used singly as one species or in a combination oftwo or more species. For easy incorporation of crosslinking points intothe acrylic polymer or for easy adjustment of the crosslink density ofthe acrylic viscoelastic material, it is preferable to use a functionalgroup-containing monomer having at least a carboxy group, a hydroxygroup or an epoxy group. Particularly preferable functionalgroup-containing monomers include a carboxy group-containing monomer anda hydroxy group-containing monomer. Favorable examples of the carboxygroup-containing monomer include acrylic acid and methacrylic acid.Favorable examples of the hydroxy group-containing monomer include2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate.

When a functional group-containing monomer as described above is used,the amount of the functional group-containing monomer (preferably acarboxyl group-containing monomer) accounts for preferably about 1% to10% by weight (e.g. about 2% to 8% by weight, typically about 3% to 7%by weight) of all the monomers.

For instance, to increase the cohesive strength of the acrylic polymer,etc., the starting monomer mixture may comprise, as the secondarymonomer, other monomer(s) that is not the functional-group-containingmonomer. Examples of the other monomer(s) include vinyl-ester-basedmonomers such as vinyl acetate, and vinyl propionate; and aromatic vinylcompounds such as styrene, substituted styrenes (α-methyl styrene,etc.), and vinyl toluene; cycloalkyl (meth)acrylates such as cyclohexyl(meth)acrylate and isobornyl (meth)acrylate; aromatic ring-containing(meth)acrylates such as aryl (meth)acrylates (e.g. phenyl(meth)acrylate), aryloxyalkyl (meth)acrylates (e.g. phenoxyethyl(meth)acrylate), and arylalkyl (meth)acrylates (e.g. benzyl(meth)acrylate); olefinic monomers such as ethylene, propylene,isoprene, butadiene, and isobutylene; chlorine-containing monomers suchas vinyl chloride and vinylidene chloride; vinyl ether-based monomerssuch as methyl vinyl ether and ethyl vinyl ether. These can be usedsingly as one species or in a combination of two or more species. Theamount of secondary monomers other than the functional group-containingmonomer can be suitably selected in accordance with the purpose andapplication, and is not particularly limited. For instance, it ispreferably about 20% or less (e.g. about 2% to 20%, typically about 3%to 10%) by weight of all the monomers for synthesizing the acrylicpolymer.

The method for synthesizing the acrylic polymer (acrylic randomcopolymer) from the monomer mixture is not particularly limited. Ageneral polymerization method can be suitably employed, such asheretofore known solution polymerization, emulsion polymerization, bulkpolymerization, and suspension polymerization. The embodiment of thepolymerization is not particularly limited. It can be carried out withsuitable selection of a heretofore known monomer supply method,polymerization conditions (temperature, time, pressure, etc.), and othercomponents (polymerization initiator, surfactant, etc.) used besides themonomer(s).

The polymerization initiator is not particularly limited. Examplesinclude an azo-based initiator such as 2,2′-azobisisobutylonitrile; aperoxide-based initiator such as benzoyl peroxide; a substitutedethane-based initiator such as phenyl-substituted ethane; and a redoxinitiator system by a combination of a peroxide and a reducing agent(e.g. a combination of a peroxide and sodium ascorbate). The amount ofpolymerization initiator used can be suitably selected in accordancewith the species of polymerization initiator, the monomer species (thecomposition of the monomer mixture) and so on. It is usually suitablyselected from a range of, for instance, about 0.005 part to 1 part byweight to 100 parts by weight of all the monomers. The polymerizationtemperature can be, for example, around 20° C. to 100° C. (typically 40°C. to 80° C.).

The weight average molecular weight (Mw) of the acrylic random copolymeris not particularly limited. For instance, an acrylic random copolymerwith Mw of about 30×10⁴ to 100×10⁴ can be favorably used as the basepolymer. In a preferable embodiment, the second layer can be an acrylicviscoelastic layer formed from a solvent-based composition thatcomprises, as the base polymer, an acrylic random copolymer with Mw inthis range.

(Acrylic Block Copolymer)

The acrylic polymer according to another preferable embodiment is anacrylic block copolymer. The acrylic block copolymer typically has atleast one hard segment A (or an “A block” hereinafter) and at least onesoft segment B (or a “B block” hereinafter) in one molecule. In thestructure of the acrylic block copolymer, the hard segment A refers tothe relatively hard block in relation to the soft segment B in theacrylic copolymer. The soft segment B refers to the relatively softblock in relation to the hard segment A in the structure of the acrylicblock copolymer.

The acrylic block copolymer may exhibit characteristics of thermoplasticpolymers (typically thermoplastic elastomers). The acrylic viscoelasticmaterial disclosed herein comprises the acrylic block copolymer as thebase polymer and thus may be a viscoelastic material suited for hot meltapplication (i.e. a hot melt viscoelastic material). From the standpointof the productivity and reduction of environmental burden, it ispreferable to use a hot melt viscoelastic material to form the secondlayer.

Here, the acrylic block copolymer refers to a block copolymer comprisinga monomer unit derived from an acrylic monomer. For instance, in apreferable acrylic block copolymer, a monomer unit derived from anacrylic monomer accounts for 50% by weight or more of the total monomerunits. Such an acrylic block copolymer can be preferably derived from astarting monomer mixture comprising, as the primary monomer, an alkyl(meth)acrylate having an alkyl group.

A preferable acrylic block copolymer comprises at least one acrylateblock (which hereinafter may be referred to as an Ac block) and at leastone methacrylate block (which hereinafter may be referred to as an MAcblock) in one molecule. For instance, a preferable block copolymer has astructure in which Ac blocks and MAc blocks are positioned alternately.The total block number of Ac blocks and MAc blocks comprised in onepolymer molecule can be about 2.5 to 5 (e.g. about 2.7 to 3.3, typicallyabout 3) in average.

In an embodiment of the Ac block, alkyl acrylate-derived monomer unitspreferably account for about 50% by weight or more of all the monomerunits forming the Ac block. Alkyl acrylate-derived monomer units mayaccount for about 75% by weight or more (e.g. about 90% by weight ormore) as well. In a preferable embodiment, the Ac block in the acrylicblock copolymer is a polymer essentially formed of one, two or morespecies (typically one species) of alkyl acrylate. Alternatively, the Acblock may be a copolymer of an alkyl acrylate and other monomer (e.g. analkyl methacrylate, etc.).

An example of the Ac block-forming alkyl acrylate is an alkyl acrylatewhose alkyl group has 1 to 20 carbon atoms (i.e. a C₁₋₂₀ alkylacrylate). Examples of the C₁₋₂₀ alkyl acrylate include methyl acrylate,ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate(BA), isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, n-hexylacrylate, n-heptyl acrylate, n-octyl acrylate, isooctyl acrylate (IOA),2-ethylhexyl acrylate (2EHA), n-nonyl acrylate, isononyl acrylate (INA),decyl acrylate, lauryl acrylate, stearyl acrylate, etc. These can beused singly as one species or in a combination of two or more species. Apreferable Ac block comprises a C₄₋₁₄ alkyl acrylate as the monomerunit. A more preferable Ac block comprises a C₄₋₉ alkyl acrylate (e.g.at least BA or 2EHA) as the monomer unit. The Ac block may comprise aC₆₋₉ alkyl acrylate as the monomer unit.

In a preferable embodiment, 50% by weight or more of monomersconstituting the Ac block is an alkyl acrylate having 4 to 14 carbonatoms in its alkyl group. The ratio of alkyl acrylate having 4 to 14carbon atoms in alkyl group can be 75% by weight or greater or can beessentially 100% by weight (e.g. greater than 99% by weight, but 100% byweight or less). For instance, it is preferable to use a structure inwhich the monomer unit(s) constituting the Ac block essentially consistof BA or 2EHA, or comprise the two species, BA and 2EHA, and so on.

In an embodiment where the Ac block-constituting monomer units compriseboth BA and 2EHA, the weight ratio of BA to 2EHA is not particularlylimited. In the monomer units, the BA/2EHA weight ratio can be, forinstance, 10/90 to 90/10, preferably 80/20 to 20/80, more preferably30/70 to 70/30, or even 60/40 to 40/60.

In an embodiment of the MAc block, alkyl methacrylate-derived monomerunits preferably account for about 50% by weight or more of all themonomer units constituting the MAc block. Alkyl methacrylate-derivedmonomer units may account for about 75% by weight or more (e.g. about90% by weight or more) as well. In a preferable embodiment, the MAcblock in the acrylic block copolymer is a polymer essentially formed ofone, two or more species (typically one species) of alkyl methacrylate.Alternatively, the MAc block may be a copolymer of an alkyl methacrylateand other monomer(s) (e.g. an alkyl acrylate, etc.).

The alkyl methacrylate constituting the MAc block may be an alkylmethacrylate whose alkyl group has 1 to 20 (preferably 1 to 14) carbonatoms. Specific examples thereof include methyl methacrylate, ethylmethacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentylmethacrylate, n-hexyl methacrylate, n-heptyl methacrylate, n-octylmethacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, n-nonylmethacrylate, isononyl methacrylate, decyl methacrylate, laurylmethacrylate, stearyl methacrylate, etc. These can be used singly as onespecies or in a combination of two or more species.

In a preferable embodiment, about 50% by weight or more of the monomersconstituting the MAc block is an alkyl methacrylate having an alkylgroup with 1 to 4 (preferably 1 to 3) carbon atoms. The ratio of thealkyl methacrylate having 1 to 4 carbon atoms in its alkyl group can beabout 75% by weight or greater, or essentially 100% by weight (e.g.greater than 99% by weight, but 100% by weight or less). Especiallypreferable alkyl methacrylates include methyl methacrylate (MMA) andethyl methacrylate (EMA). For example, the monomers preferably employedmay consist essentially of MMA alone, EMA alone, both MMA and EMA, orthe like.

The acrylic block copolymer may be a copolymer comprising A blocks (hardsegments A) and B blocks (soft segments B) placed alternately, with theA block having been formed of a polymer having a rigid structure withexcellent cohesive strength and elasticity, and the B block having beenformed of a polymer having a flexible structure with excellentviscosity. With a viscoelastic material comprising as its base polymeran acrylic block copolymer having such a structure, the second layer maybe formed with cohesive strength, elasticity, and viscosity combined ata high level. A viscoelastic material having such a composition can bepreferably used as a hot melt viscoelastic material. In the hot meltviscoelastic material, an acrylic block copolymer having a structurewith an A block at each terminus can be preferably used. An acrylicblock copolymer having such a structure is likely to exhibitwell-balanced cohesion and thermoplasticity. From the standpoint ofreducing the melt viscosity, etc., an acrylic block copolymer having alinear structure is advantageous as compared to a species having astellar structure or a branched structure.

When the acrylic block copolymer comprises two or more A blocks, thecompositions, molecular weights (polymerization degrees), structures,etc., of these A blocks can be the same with or different from eachother. When the acrylic block copolymer comprises two or more B blocks,the same applies to the B blocks.

As the A block, a MAc block as those described above can be preferablyused. As the B block, an Ac block as those described above can bepreferably used. In a preferable embodiment, the acrylic block copolymeris a triblock copolymer having a structure of MAc-Ac-MAc (ABAstructure). For instance, can be preferably used a triblock copolymerwith two MAc blocks having essentially identical monomer compositions.

In an embodiment, a preferable acrylic block copolymer has a softsegment B that comprises a monomer unit derived from a C₆₋₉ alkylacrylate. Specific examples of the C₆₋₉ alkyl acrylate include 2EHA,n-octyl acrylate, n-nonyl acrylate, INA, and IOA. With respect to suchan alkyl acrylate, its homopolymer generally has a low glass transitiontemperature (Tg). Thus, when it is used as a monomer forming an Acblock, it enhances the low-temperature properties of an acrylic blockcopolymer having the Ac block and may further enhance thelow-temperature properties (e.g. the flexibility at a low temperature)of a viscoelastic material (the second layer) comprising the acrylicblock copolymer as the base polymer. This may result in a smallerincrease in unwinding force at a low temperature, reducing the unwindingforce ratio (F₀/F₃₀). These effects can be greater with a C₆₋₉ alkylacrylate whose homopolymer has a Tg of lower than −55° C. (morepreferably about −60° C. or lower, e.g. about −65° C. or lower). TheC₆₋₉ alkyl acrylates exemplified above have the following Tg values:2EHA −70° C., n-octyl acrylate −65° C., n-nonyl acrylate −60° C., INA−58° C., and IOA −58° C.

Of the monomer units forming the Ac block, the amount of the C₆₋₉ alkylacrylate can be, for instance, about 10% by weight or greater. It ispreferably about 20% or greater, more preferably about 30% or greater,or yet more preferably about 40% or greater, by weight. The monomerunits forming the Ac block may consist of one, two or more species ofC₆₋₉ alkyl acrylate. From the standpoint of the cohesion of the acrylicviscoelastic material, etc., the C₆₋₉ alkyl acrylate can be used in anamount of about 90% by weight or less, about 75% by weight or less, oreven about 60% by weight or less of the monomer units forming the Acblock.

In an embodiment, it is possible to use an acrylic block copolymer thathas, as the soft segment B, an Ac block formed with monomer units thatcomprise an alkyl acrylate whose alkyl group has 6 or more (e.g. 6 to12, typically 6 to 9) carbon atoms and an alkyl acrylate whose alkylgroup has 2 to 5 (e.g. 3 to 4, typically 4) carbon atoms at a weightratio of 20/80 to 80/20 (more preferably 30/70 to 70/30, or yet morepreferably 40/60 to 60/40, e.g. 45/55 to 55/45). Such an acrylic blockcopolymer may have well-balanced low-temperature properties andcohesiveness. For instance, it is preferable to use an acrylic blockcopolymer that has, as the soft segment B, an Ac block formed withmonomer units that comprise 2EHA and BA at an aforementioned weightratio. The Ac block may be formed solely from 2EHA and BA.

The weight ratio of hard segment A to soft segment B is not particularlylimited in the acrylic block copolymer. The weight ratio (A/B) of hardsegment A to soft segment B can be in a range of, for instance, 4/96 to90/10, or it is usually suitably in a range of 7/93 to 70/30 orpreferably in a range of 10/90 to 50/50 (e.g. more preferably 15/85 to40/60, e.g. 15/85 to 25/75). In the acrylic block copolymer comprisingtwo or more hard segments A, the ratio of total weight of these hardsegments A to weight of soft segment B is preferably in these ranges.The same applies to the acrylic block copolymer comprising two or moresoft segments B. A high ratio of hard segments A (e.g. MAc blocks) islikely to decrease the flexibility at a low temperature, increasing theunwinding force at a low temperature (e.g. 0° C.); and the unwindingforce tends to show higher temperature-dependence. A high ratio of softsegments B (e.g. Ac blocks) tends to lower the cohesion of the acrylicviscoelastic material.

In a preferable example of the acrylic block copolymer disclosed herein,the starting monomers corresponding to all the monomer unitsconstituting the acrylic block copolymer comprise an alkyl(meth)acrylate m_(X) having 1 to 3 carbon atoms in its alkyl group andan alkyl (meth)acrylate m_(Y) having 6 or more (e.g. 6 to 12) carbonatoms in its alkyl group. The weight ratio m_(X)/m_(Y) can be, forinstance, 4/96 to 90/10. An acrylic block copolymer with the weightratio being 7/93 to 70/30 is preferable, a species with 10/90 to 50/50is more preferable, a species with 15/85 to 40/60 is yet morepreferable, and a species with 15/85 to 30/70 (e.g. 15/85 to 25/75) isparticularly preferable. A high ratio of m_(X) tends to reduce theunwinding force and facilitate withdrawal (unwinding) of the PSA tapefrom the PSA tape roll. As the m_(X), an alkyl methacrylate whose alkylgroup has one to three carbon atoms is preferable. For instance, MMA ispreferable. When the ratio of m_(Y) is high, roll-loosening is likely tobe inhibited. As the m_(Y), an alkyl acrylate whose alkyl group has atleast six (e.g. 6 to 12, preferably 6 to 9) carbon atoms is preferable.For instance, 2EHA is preferable.

The composition of monomer units constituting an acrylic block copolymercan be determined based on the results of NMR analysis. In particular,the NMR analysis can be carried out, using, for instance, AVAVCEIII-600(with Cryo Probe) available from Bruker Biospin as the NMR system, underthe conditions shown below. For instance, the weight ratio of MMA to2EHA in the starting monomers can be determined based on the ratio ofintegrated intensities of peaks at 4.0 ppm (2EHA1) and 3.6 ppm (MMA1) inthe ¹H NMR spectrum.

[NMR Analysis Conditions]

Measurement frequency: ¹H; 600 MHz

Flip angle: 30°

Measurement solvent: CDCl₃

Measurement temperature: 300 K

Standard chemical shift: measurement solvent (CDCl₃, ¹H: 7.25 ppm)

The acrylic block copolymer's Mw is not particularly limited. Forinstance, an acrylic block copolymer having a Mw of about 3×10⁴ to30×10⁴ can be preferably used. Usually, the acrylic block copolymer hasa Mw in a range of preferably about 3.5×10⁴ to 25×10⁴ or more preferablyin a range of about 4×10⁴ to 20×10⁴ (e.g., 4.5×10⁴ to 15×10⁴). A high Mwof the acrylic block copolymer is advantageous from the standpoint ofincreasing the cohesion of the acrylic viscoelastic material andincreasing the ability to collect dust on the target surface. On theother hand, a low Mw of the acrylic block copolymer is advantageous fromthe standpoint of decreasing the melt viscosity or the solutionviscosity. It is particularly significant to decrease the melt viscosityof the acrylic viscoelastic material in an embodiment where the secondlayer is formed by hot melt coating of the viscoelastic material.

The Mw of an acrylic block copolymer herein refers to the value based onstandard polystyrene that is determined by gel permeation chromatography(GPC) with respect to a sample prepared by dissolving the copolymer intetrahydrofuran (THF). In particular, the GPC measurement can beperformed, using, for instance, trade name “HLC-8120GPC” available fromTosoh Corporation as the GPC measurement system, under the conditionsshown below. The Mw values of the other polymer and oligomer describedlater can be determined in the same manner.

[GPC Measurement Conditions]

Columns: available from Tosoh Corporation, TSK gel SuperHZM-H/HZ4000/HZ3000/HZ2000

Column size: 6.0 mm I.D.×150 mm each

Eluent: THF

Flow rate: 0.6 mL/min

Detector: differential refractometer (RI)

Column temperature (measurement temperature): 40° C.

Sample concentration: about 2.0 g/L (THF solution)

Sample injection volume: 20 μL

In the acrylic block copolymer in the art disclosed herein, a monomer(other monomer) other than an alkyl(meth)acrylate may be copolymerized.Examples of the other monomer include vinyl compounds having functionalgroups such as alkoxy group, epoxy group, hydroxy group, amino group,amide group, cyano group, carboxyl group, acid anhydride group, etc.;vinyl esters such as vinyl acetate; aromatic vinyl compounds such asstyrene; vinyl group-containing heterocyclic compounds such asN-vinylpyrrolidone and the like. Alternatively, it can be an alkylacrylate having a structure with an acryloyl group coupled to afluorinated alkyl group, a fluorinated alkyl acrylate and a fluorinatedalkyl methacrylate. The other monomer may be used, for instance, toadjust the properties of the acrylic viscoelastic material. The othermonomer content is suitably 20% by weight or less (e.g. 10% by weight orless, typically 5% by weight or less) of all the monomers constitutingthe acrylic block copolymer. In a preferable embodiment, the acrylicblock copolymer is essentially free of the other monomers. For instance,in a preferable acrylic block copolymer, the other monomer content isless than 1% by weight (typically 0 to 0.5% by weight) of all monomersor under the detection limit.

Such an acrylic block copolymer can be readily synthesized by a knownmethod (e.g. see Japanese Patent Application Publication Nos.2001-234146 and H11-323072), or a commercial product is readilyavailable. Examples of the commercial product include trade nameKURARITY series (e.g., those with product numbers LA2140e, LA2250, etc.)available from Kuraray Co., Ltd., trade name “NABSTAR” available fromKaneka Corporation, and the like. As the method for synthesizing theacrylic block copolymer, living polymerization method can be preferablyemployed. According to living polymerization, while keeping theweatherability inherent in the acrylic polymer, an acrylic blockcopolymer having excellent thermoplasticity can be synthesized due tothe excellent structure control unique to the living polymerization. Inaddition, since the molecular weight distribution can be controlled in anarrow range, insufficient cohesion caused by the presence of lowmolecular weight components can be prevented, whereby the second layerwith excellent anti-loosening properties can be obtained.

For the acrylic block copolymer, solely one species or a combination oftwo or more species can be used. For instance, an acrylic blockcopolymer B_(H) with a relatively high Mw and an acrylic block copolymerB_(L) with a lower Mw than the acrylic block copolymer B_(H) can be usedat a suitable weight ratio. For instance, it is preferable to combine aB_(H) having a Mw in a range of 5×10⁴ to 20×10⁴ (e.g. 7×10⁴ to 20×10⁴)and a B_(L) having a Mw in a range of 3×10⁴ to 8×10⁴ and lower than theMw of the B_(H). The B_(H) to B_(L) weight ratio (B_(H)/B_(L)) is notparticularly limited and can be, for instance, in a range of 5/95 to95/5, 10/90 to 90/10, 40/60 to 90/10, or even 55/45 to 90/10. Theinclusion (presence) of two or more species of acrylic block copolymerwith different Mw values, the Mw values of the respective acrylic blockcopolymers and their weight ratio can be assessed, for instance, by GPCanalysis as described earlier.

In addition to the acrylic polymer, the viscoelastic material formingthe second layer may comprise a non-acrylic polymer as an optionalcomponent in order to enhance the low-temperature properties, reduce theadhesive strength, to enhance the handling properties, to improve theproductivity, etc. Examples of such a polymer (or the optional polymerhereinafter) include polyolefins, polyesters, vinyl acetate-basedpolymers and vinyl chloride-based polymers. These polymers can be usedsingly as one species or in a combination of two or more species. Theoptional polymer content per 100 parts by weight of the acrylic polymercan be selected in accordance with the purpose or a particularcircumstance. For instance, it can be 100 parts by weight or less, about70 parts by weight or less, about 50 parts by weight or less, about 30parts by weight or less, about 10 parts by weight or less, or even about5 parts by weight or less. The viscoelastic material forming the secondlayer can be essentially free of an optional polymer. For instance, theoptional polymer content per 100 parts by weight of the acrylic polymercan also be less than 1 part (typically 0 to 0.5 part) by weight.

(Oligomer)

In the art disclosed herein, the viscoelastic material forming thesecond layer may comprise an oligomer as an optional component foradjusting the viscosity (e.g. lowering the melt viscosity), controllingthe adhesive properties of the PSA tape roll (e.g. reducing the adhesivestrength), improving the operational feeling (e.g. the response from theresistance associated with rolling of the tape roll over the targetsurface), etc. The Mw of the oligomer is not particularly limited. It istypically about 30000 or less. In an embodiment, the oligomer's Mw canbe about 20000 or less, or even about 10000 or less (e.g. about 5000 orless). The oligomer's Mw can be about 300 or greater, or even about 500or greater (e.g. about 800 or greater).

The oligomer is not particularly limited. Known acrylic oligomer,urethane-based oligomer, acrylic urethane-based oligomer, siliconeacrylic oligomer, organosiloxane-based oligomer, polyester-basedoligomer, polyolefinic oligomer, vinyl ether-based oligomer and the likecan be used. The oligomers can be used singly as one species or in acombination of two or more species. The oligomer used can be produced bya known method or commercial products are readily available.

From the standpoint of the compatibility with the base polymer, in anembodiment, a preferable oligomer comprises a monomer unit derived froman acrylic monomer, such as an acrylic oligomer and an acrylicurethane-based oligomer. The acrylic monomer content of the monomersforming the oligomer is typically about higher than 50% by weight,preferably about 70% by weight or higher, more preferably about 85% byweight or higher, possibly about 90% by weight or higher, or it can beessentially 100% by weight. The acrylic oligomer can be a randomcopolymer of a starting monomer mixture comprising an acrylic monomer asthe primary component.

When an oligomer is used, its amount used is not particularly limited.In an embodiment, the amount of the oligomer used to 100 parts by weightof the base polymer can be, for instance, about 150 parts by weight orless, and usually suitably about 100 parts by weight or less (e.g. about80 parts by weight or less). To 100 parts by weight of the base polymer,the amount of the oligomer used can be, for instance, about 5 parts byweight or greater, about 10 parts by weight or greater, or even about 20parts by weight or greater (e.g. about 30 parts by weight or greater).In another embodiment, the amount of the oligomer used to 100 parts byweight of the base polymer can be, for instance, about 25 parts byweight or less, or even about 10 parts by weight or less (e.g. about 5parts by weight or less). The art disclosed herein can be preferablyimplemented in an embodiment where the acrylic viscoelastic materialforming the second layer is essentially free of an oligomer. Forinstance, the oligomer content per 100 parts by weight of the basepolymer can be less than 1 part (typically 0 to 0.5 part) by weight.

(Filler)

In the art disclosed herein, the viscoelastic material forming thesecond layer may comprise a filler. The inclusion of the filler in thesecond layer can bring about effects such as lowertemperature-dependence of the unwinding force, reduced adhesivestrength, enhanced anchoring, and easier hand-tearing of the PSA tape.

The type of filler used is not particularly limited. For instance,particulate or fibrous filler can be used. Examples of the materialforming the filler (typically particulate filler) include inorganicmaterials such as carbonates including calcium carbonate, sodiumcarbonate, and sodium bicarbonate; metal oxides including titaniumoxide, silica, alumina, zirconia, zinc oxide, tin oxide, copper oxide,and nickel oxide; metal hydroxides and hydrated metal compoundsincluding aluminum hydroxide, boehmite, talc, magnesium hydroxide,calcium hydroxide, zinc hydroxide, silicate, iron hydroxide, copperhydroxide, barium hydroxide, hydrated zirconium oxide, hydrated tinoxide, basic magnesium carbonate, hydrotalcite, dawsonite, borax, andzinc borate; carbides including silicon carbide, boron carbide, nitrogencarbide, and calcium carbide; nitrides including aluminum nitride,silicon nitride, boron nitride, and gallium nitride; titanates includingbarium titanate and potassium titanate; carbonaceous substancesincluding carbon black, carbon tube (carbon nanotube), carbon fibers,and diamond; and glass; metals such as copper, silver, gold, platinum,nickel, aluminum, chromium, iron, and stainless steel; and polymers suchas polystyrene, acrylic resin (e.g. polymethyl methacrylate), phenolresin, benzoguanamine resin, urea resin, silicone resin, polyester,polyurethane, polyethylene, polypropylene, polyamide (e.g. nylon, etc.),polyimide, and polyvinylidene chloride. Alternatively, particles of anatural raw material can also be used, such as volcanic shirasu (ash),clay and sand. As the fibrous filler, various synthetic fibers andnatural fibers can be used. These can be used singly as one species orin a combination of two or more species. A pigment can be used as partof or as the entirety of the filler. The pigment can be inorganic ororganic. Similarly, the PSA forming the first layer may have afiller-containing composition.

While no particular limitations are imposed, the average particlediameter of the filler can be, for instance, about 100 μm or smaller,about 50 μm or smaller, or even about 30 μm or smaller (e.g. about 15 μmor smaller). From the standpoint of the ease of forming the second layerand its surface smoothness, the average particle diameter of the filleris preferably about 70% or less (typically about 50% or less, e.g. about30% or less) of the thickness of the second layer. From the standpointof the dispersibility and the handleability of the filler, a fillerhaving an average particle diameter of about 0.01 μm or larger(typically about 0.1 μm or larger, e.g. about 1 μm or larger) can bepreferably used.

In an embodiment where the viscoelastic material forming the secondlayer comprises a filler, the percent weight of the filler in the secondlayer (the weight ratio of the filler in the second layer) is notparticularly limited, and can be selected so as to obtain desirableeffects. The percent weight can be, for instance, about 0.1% or higher(typically about 0.5% or higher), about 1% or higher, about 3% orhigher, about 5% or higher, or even about 10% or higher. In anembodiment of the art disclosed herein, the percent weight of the fillerin the second layer can be about 20% or higher, or even about 30% orhigher (e.g. about 40% or higher). From the standpoint of the ease offorming the second layer and the retention of the shape, the percentweight of the filler is usually suitably about 75% or lower, orpreferably about 60% or lower (e.g. about 50% or lower). In anembodiment, the percent weight of the filler can also be lower than 10%,for instance, lower than 5%. The component(s) other than the filler inthe second layer can be thought as elastomers (non-hard components).Accordingly, the percent (%) weight R of the elastomer content in thefiller-containing second layer can be thought as the value obtained bysubtracting the percent weight of the filler in the second layer from100%. In the second layer free of a filler, the percent (%) weight R ofthe elastomer content is 100%.

(Tackifier)

The viscoelastic material forming the second layer can comprise atackifier as necessary. The tackifier may be useful in adjusting theadhesive strength as well as in increasing the thermoplasticity of theviscoelastic material (e.g. decreasing the melt viscosity), etc. As thetackifier, a tackifier resin known in the field of PSA (e.g. acrylicPSA) and the like can be used. Examples include a hydrocarbon-basedtackifier resin, terpene-based tackifier resin, rosin-based tackifierresin, phenolic tackifier resin, epoxy-based tackifier resin,polyamide-based tackifier resin, elastomer-based tackifier resin andketone-based tackifier resin. These can be used singly as one species orin a combination of two or more species. Similarly, the PSA forming thefirst layer may have a composition that comprises a tackifier.

The softening point of the tackifier is not particularly limited. Fromthe standpoint of reducing the melt viscosity, it is preferably about160° C. or lower, or more preferably about 140° C. or lower (e.g. about120° C. or lower). From the standpoint of the low-temperature properties(e.g. the flexibility at a low temperature) of the second layer, atackifier having a softening point of about 100° C. or lower (e.g. about80° C. or lower) can be used as well. The tackifier typically has asoftening point of 60° C. or higher. The softening point of thetackifier is determined based on the softening point test method (ringand ball method) specified in JIS K 2207.

When a tackifier is used, its amount used is not particularly limited.In an embodiment, the amount of the tackifier used to 100 parts byweight of the base polymer can be about 1 part by weight or greater, oreven about 5 parts by weight or greater (e.g. about 10 parts by weightor greater). From the standpoint of avoiding degradation of thelow-temperature properties, the amount of the tackifier is usuallysuitably about 50 parts by weight or less to 100 parts by weight of thebase polymer, or preferably about 30 parts by weight or less (e.g. about20 parts by weight or less). The second layer may be essentially free ofa tackifier.

(Plasticizer)

The viscoelastic material forming the second layer may comprise aplasticizer as necessary. The plasticizer may be useful in reducing themelt viscosity, reducing the adhesive strength, enhancing thelow-temperature properties, etc. Examples of plasticizer includephthalic acid esters such as dioctyl phthalate, diisononyl phthalate,diisodecyl phthalate, dibutyl phthalate, etc.; adipic acid esters suchas dioctyl adipate, diisononyl adipate, etc.; trimellitic acid esterssuch as trioctyl trimellitate, etc.; sebacic acid esters; epoxidizedvegetable oils such as epoxidized soybean oil and epoxidized flax seedoil; epoxidized fatty acid alkyl esters such as epoxidized fatty acidoctyl esters; cyclic fatty acid esters as well as their derivatives suchas sorbitan monolaurate, sorbitan monostearate, sorbitan monooleate,sorbitan trioleate and their ethylene oxide adducts; and the like. Thesecan be used singly as one species or in a combination of two or morespecies. Similarly, the PSA forming the first layer may have acomposition that comprises a plasticizer.

When a plasticizer is used, its amount used is not particularly limited.In an embodiment, the amount of the tackifier used to 100 parts byweight of the base polymer can be about 1 part by weight or greater,about 5 parts by weight or greeter (e.g. about 10 parts by weight orgreater). From the standpoint of preventing the plasticizer fromtransferring (migrating) to the backside of the PSA tape or to thesurface being cleaned, the amount of the plasticizer used is usuallysuitably about 100 parts by weight or less to 100 parts by weight of thebase polymer, or preferably about 50 parts by weight or less (e.g. about30 parts by weight or less). The second layer may be essentially free ofa plasticizer.

(Crosslinking Agent)

The viscoelastic material forming the second layer can be crosslinked asnecessary. For crosslinking the material, known crosslinking agents canbe used such as organometallic salts including zinc stearate and bariumstearate, epoxy-based crosslinking agents, isocyanate-based crosslinkingagent, oxazoline-based crosslinking agent, aziridine-based crosslinkingagent, metal chelate-based crosslinking agent and melamine-basedcrosslinking agent. The crosslinking agents can be used singly as onespecies or in a combination of two or more species. The amount of thecrosslinking agent used is not particularly limited. In an embodiment,the amount of the crosslinking agent used to 100 parts by weight of thebase polymer can be about 0.01 part by weight or greater (typicallyabout 0.02 part by weight or greater, e.g. 0.05 part by weight orgreater) and about 10 parts by weight or less (e.g. about 5 parts byweight or less). The viscoelastic material may form a non-crosslinkedsecond layer without applying a specific crosslinking means. This ispreferable from the standpoint of the productive convenience, etc.

(Other Components)

To the second layer in the art disclosed herein, various additives knownin the field of acrylic viscoelastic materials (e.g. acrylic PSA) can beadded as necessary, such as anti-aging agent, antioxidant, UV absorber,photostabilizer, antistatic agent, and dye. The types of such optionaladditives and their amounts added can be comparable to usual species andamounts added with respect to these types of material.

(Elongation at Break)

The viscoelastic material forming the second layer may exhibit anelongation at break of preferably about 2000% or less, or morepreferably about 1000% or less (e.g. about 500% or less). A smallerelongation at break tends to facilitate hand-tearing of the PSA tape.From the standpoint of the flexibility and the durability of the secondlayer, the elongation at break is usually suitably about 30% or greater,or preferably about 50% or greater (e.g. about 100% or greater).

The elongation at break of the viscoelastic material is determined basedon the method for determining “Elongation” described in JIS K 7311:1995.More specifically, using a No. 3 dumbbell-shaped test piece (1 mm thick,5 mm wide, 10 mm line spacing), the elongation at break can bedetermined at a tensile speed of 300 mm/min. As the tensile tester,product name AUTOGRAPH AG-10G tensile tester available from ShimadzuCorporation can be used. For the testing, the adhesive face ispreferably covered with powder to eliminate influences of the stickinessof the PSA. The same method is also employed in Examples describedlater. The elongation at break can be adjusted, for instance, by thecomposition of the viscoelastic material forming the second layer(selection of the types of components in the viscoelastic material andtheir amounts, etc.).

(Breaking Strength)

The breaking strength of the viscoelastic material forming the secondlayer is not particularly limited. It is usually suitably about 50 N/10mm or less, or can be about 20 N/10 mm or less (e.g. about 10 N/10 mm orless). Smaller breaking strength tends to facilitate hand-tearing of thePSA tape. From the standpoint of the durability of the second layer,etc., the breaking strength is usually suitably about 1 N/10 mm orgreater, or can be about 2 N/10 mm or greater (e.g. about 3 N/10 mm orgreater).

The breaking strength of the viscoelastic material is determined basedon the method for determining “Tensile Strength” described in JIS K7311:1995 as the value per 10 mm width of the viscoelastic materialsubjected to the measurement (i.e. as the value in N/10 mm). Morespecifically, using a No. 3 dumbbell-shaped test piece (1 mm thick, 5 mmwide, 10 mm line spacing), the breaking strength can be determined at atensile speed of 300 mm/min. The tensile tester and other conditions arebasically the same as for the elongation at break. The same method isused in Examples described later. The breaking strength can be adjusted,for instance, by the composition of the viscoelastic material formingthe second layer (selection of the types of components in theviscoelastic material and their amounts, etc.).

(AR Value)

The art disclosed herein can be preferably implemented in an embodimentwhere the product of the cross-sectional area A (mm²) of the secondlayer in a widthwise cross section of the PSA tape times the percent (%)weight R of the elastomer content in the second layer (i.e. the value ofA·R, or the AR value hereinafter) is about 2.5 or less. In such anembodiment, hand-tearing of the PSA tape may be facilitated. Forinstance, when the PSA tape is torn off, formation of sticky strings ofthe second layer can be inhibited. Formation of sticky strings mayoccur, in typical, in an embodiment where a line of the second layerruns across an expected tear-off location in the PSA tape. When the PSAtape is torn off, the substrate is torn apart while the second layer isnot, whereby the second layer is stretched between the two separatepieces of the substrate to form sticky strings. Significant stringinessleads to issues such as difficult tearing and degraded appearance. Withthe stretched part of the second layer forming the renewed adhesive face(the adhesive face exposed upon the tearing on the surface of the PSAtape roll), the surface state of the adhesive face may be distorted. Bylimiting the AR value, the stringiness of the second layer may besuppressed.

The cross-sectional area A (mm²) of the second layer can be, forinstance, about 0.001 mm² or larger; it is usually suitably about 0.005mm² or larger, also about 0.007 mm² or larger, or even about 0.01 mm² orlarger. In an embodiment, the cross-sectional area A (mm²) of the secondlayer can be about 0.015 mm² or larger, or even about 0.02 mm² orlarger. The cross-sectional area A (mm²) of the second layer can be, forinstance, about 5 mm² or smaller; it is usually suitably about 1 mm² orsmaller, possibly about 0.5 mm² or smaller, about 0.1 mm² or smaller, oreven about 0.05 mm² or smaller. In an embodiment, the cross-sectionalarea A (mm²) of the second layer may be about 0.03 mm² or smaller (e.g.about 0.02 mm² or smaller).

Here, the cross-sectional area A (mm²) of the second layer refers to thesurface area of the second layer that appears in a widthwise crosssection of the PSA tape. The cross-sectional area of the second layercan be obtained, for instance, by analyzing the cross section with ascanning electron microscope. With respect to the second layer formed inlines running in the length direction of the PSA tape, thecross-sectional area of the second layer may be determined from theweight of the second layer contained per unit length of the PSA tape andthe specific gravity of the second layer. In determining the AR value, Arefers to the numerical value of the cross-sectional area (in mm²) ofthe second layer, but without the unit. In determining the AR value, Rrefers to the numerical value of the percent (%) weight of the elastomercontent in the viscoelastic material forming the second layer, butwithout the unit. Thus, the AR value is a dimensionless number.

In the art disclosed herein, the AR value is preferably about 2.3 orless, more preferably about 2.1 or less, or can be about 2.0 or less(e.g. about 1.7 or less). With decreasing AR value, formation of stickystrings of the second layer tends to be further suppressed. The minimumAR value is not particularly limited. For instance, it can be about 0.1or greater. From the standpoint of the ease of forming the second layerand the retention of its shape, the AR value is usually suitably about0.3 or greater, or can also be about 0.5 or greater (e.g. about 0.7 orgreater). In an embodiment, the AR value can be about 1.0 or greater(e.g. about 1.2 or greater). The AR value can be adjusted by the linewidth and the thickness of the second layer in a widthwise cross sectionof the PSA tape, the amount of the filler used in the second layer, etc.

(Rotational Resistance)

The PSA tape roll disclosed herein has a rotational resistance ofpreferably about 3 N/150 mm or greater (e.g. about 4 N/150 mm orgreater). The rotational resistance is preferably about 12 N/150 mm orless, or about 15 N/150 mm or less. The PSA tape roll with such a levelof rotational resistance is preferable since favorable operationalfeeling is likely to be provided. For instance, when it is rolled over asurface to be cleaned, it provides a suitable response (resistance)against operation, whereby a user is more likely to feel assured ofcleaning effects. When the rotational resistance is not excessivelyhigh, the load on a user is reduced and rail drawing is less likely tooccur. The rotational resistance can be determined by the methoddescribed later in Examples. The PSA tape roll satisfying the rotationalresistance on more diverse surfaces (e.g. carpet, waxed flooringsurface, wax-free flooring surface, etc.) to be cleaned is preferable.

Second Embodiment

FIG. 5 shows a cross-sectional diagram schematically illustrating thePSA tape forming the PSA tape roll in another embodiment of thisinvention. PSA tape 112 has a substrate 120, a first layer 131 directlyprovided onto the first face 120A thereof, and a second layer 132directly provided onto the first face 120A without overlapping the firstlayer 131. The first layer 131 can be formed from a PSA (e.g. arubber-based PSA) comparable to that of the first layer in the firstembodiment. The second layer 132 can be formed from a viscoelasticmaterial (typically an acrylic viscoelastic material, e.g. an acrylicPSA) comparable to the second layer in the first embodiment.

In the present embodiment, PSA tape 112 has straight lines of the secondlayer 132 running in the length direction of PSA tape 112 and theselines of the second layer 132 are arranged almost in parallel to oneanother (in a stripe pattern), separated by spaces in the widthdirection of the PSA tape 112. The PSA tape 112 in this embodiment hasstraight lines of the first layer 131 running in the length direction ofPSA tape 112. The respective lines of the first layer 131 are arrangedalmost in parallel to one another (in a stripe pattern) between adjacentlines of the second layer 132. In other words, lines of the first layer131 and lines of the second layer 132 are arranged alternately whenviewed across the width. The first sections 131A where the first layer131 is exposed and the second sections 132A where the second layer 132is exposed form the adhesive face 135 which is adhesive as a whole. Thewidth (W2 in FIG. 5) of the second layer can be selected from acomparable range to the width range of the second layer in the firstembodiment described earlier.

The width (W1 in FIG. 5) of the first layer 131 can be, for instance,about 0.1 mm or greater, also about 0.3 mm or greater, or even about 0.5mm or greater. The width W1 of the first layer 131 can be, for instance,about 50 mm or less; it is usually suitably about 20 mm or less, about10 mm or less, about 5 mm or less, about 1 mm or less, or even about 0.5mm or less. By adjusting W1, the unwinding force and the operationalfeeling during use can be adjusted. When the line width of the firstlayer 131 changes from place to place, the aforementioned ranges of W1values can be applied to the average line width over a certain length.

While no particular limitations are imposed, the width W1 of the firstlayer can be, for instance, about 0.5 times to 20 times (typically 1times to 10 times) the width W2 of the second layer; it is usuallysuitably about 1 times to 5 times. In an embodiment, W1 can be greaterthan W2 (i.e. W1>W2). For instance, W1 can be at least about 1.1 timesW2, also at least about 1.3 times W2, or even at least about 1.5 timesW2.

The first layer 131 and the second layer 132 can be formed so that thethickness T12 of the second layer 132 is greater than the thickness T11of the first layer 131. The difference in thickness (T12−T11) betweenthe first and second layers 131, 132 can be selected, for instance, froma range comparable to the protruding height T2 of the second sectionsrelative to the first sections in the first embodiment. The thicknessT11 of the first layer 131 can be selected from a range comparable tothe thickness T1 of the first layer in the first embodiment. Thethickness T12 of the second layer 132 can be selected from a rangecomparable to the height H from the first face of the substrate to thesecond sections in the first embodiment.

The first layers 131 and the adjacent second layers 132 may be partiallyor entirely in contact, or may be separated by a space G The presence ofthe space G between the first and second layers 131 and 132 may inhibitchanges in properties of PSA tape 112 caused by transfer (diffusion) ofcomponents from one layer to the other layer. The presence of the spaceG may contribute to the cushioning properties of PSA tape 112 and PSAtape roll 110 obtainable by winding the same.

The presence of the space G increases the surface area of the adhesiveface 135, likely enhancing the abilities to collect and store dust. Thewidth of the space G can be, for instance, 0.01 mm or greater, 0.05 mmor greater, or even 0.1 mm or greater. The width of the space G can be,for instance, 5 mm or less, 1 mm or less, or even 0.5 mm or less.

As the substrate, similarly to the substrate in the first embodiment,various types of resin film, paper, fabric, rubber sheet, foam sheet,metal foil, a composite of these and the like can be used. One or eachof the first and second faces of the substrate may be subjected asnecessary to a surface treatment as described about the firstembodiment.

From the standpoint of the strength and the flexibility, favorableexamples of the resin film possibly used as the substrate or a componentthereof include polyolefin film. The polyolefin film comprises as theprimary component a polymer whose primary monomer (the primary componentamong its monomers) is an α-olefin. The polymer content is usually 50%by weight or higher (e.g. 80% by weight or higher, typically 90% to 100%by weight). Specific examples of the polyolefin include PE whose primarymonomer is ethylene, and PP whose primary monomer is propylene. The PEcan be ethylene homopolymer, a copolymer of ethylene and other olefin(e.g. one, two or more species selected among α-olefins with 3 to 10carbon atoms), or a copolymer of ethylene and a non-olefinic monomer(e.g. one, two or more species selected from ethylenic unsaturatedmonomers such as vinyl acetate, acrylic acid, methacrylic acid, methylacrylate, and ethyl acrylate). The PP can be propylene homopolymer, acopolymer of propylene and other olefin (e.g. one, two or more speciesselected among α-olefins with 2 or 4 to 10 carbon atoms), or a copolymerof propylene and a non-olefinic monomer. The substrate disclosed hereinmay comprise solely one species of polyolefin among them or may comprisetwo or more species of polyolefin.

From the standpoint of increasing the strength, the polyolefin film maycomprise a high density polyethylene (HDPE). As used herein, the HDPEtypically refers to a polyethylene having a density of 0.940 g/cm³ orgreater. From the standpoint of increasing the strength (e.g. thetensile strength), the HDPE content in the substrate is preferably 10%by weight or higher, or more preferably 20% by weight or higher (e.g.30% by weight or higher, typically 35% by weight or higher). In view ofthe conformability to surface contours, the HDPE content in thesubstrate can be usually 80% by weight or lower (e.g. 70% by weight orlower, typically 60% by weight or lower).

From the standpoint of increasing the flexibility, the polyolefin filmmay comprise a low density polyethylene (LDPE). As used herein, the LDPErefers to a polyethylene having a density of less than 0.940 g/cm³. TheLDPE disclosed herein can be, for instance, an LDPE obtainable by highpressure polymerization of ethylene monomers, an LDPE obtainable by lowpressure polymerization of ethylene and an α-olefin monomer with 3 to 8carbon atoms, a copolymer of ethylene and an α-olefin with the copolymerhaving an aforementioned density, etc. The concept of LDPE in the artdisclosed herein encompasses species called very low densitypolyethylene (VLDPE) and species called linear low density polyethylene(LLDPE). As the LDPE, solely one species or a combination of two or morespecies can be used.

The art disclosed herein can be preferably implemented in an embodimentcomprising a substrate formed using an HDPE-containing polyolefin film(typically a PE film). From the standpoint of increasing the strength(e.g. the tensile strength), the HDPE content in the polyolefin film ispreferably 10% by weight or higher, 30% by weight or higher (e.g. 50% byweight or higher), or even 70% by weight or higher (e.g. 85% by weightor higher). A polyolefin film essentially formed of a HDPE (a polyolefinfilm of which HDPE accounts for 99% to 100% by weight) can also be used.Alternatively, in view of the flexibility of the substrate, a polyolefinfilm of which HDPE accounts for 95% by weight or less (e.g. 90% byweight or less, or even 75% by weight or less) can be used as well.

The art disclosed herein can be preferably implemented in an embodimentcomprising a substrate formed using a polyolefin film (typically apolyethylene film) comprising HDPE and LDPE. The use of such apolyolefin film as the substrate or a component thereof can combinestrength and flexibility at a high level. The combined amount of HDPEand LDPE in the polyolefin film is not particularly limited. It ispreferably 50% by weight or greater (e.g. 80% by weight or greater,typically 90% to 100% by weight). The art disclosed herein can bepreferably implemented in an embodiment where the polyolefin film isessentially free of other materials besides the HDPE and the LDPE. WhenHDPE and LDPE are used together, the weight ratio of HDPE to LDPE in thesubstrate is not particularly limited, but is usually about 10:90 to90:10, or preferably 20:80 to 80:20 (e.g. 30:70 to 70:30, typically35:65 to 65:35).

The polyolefin film may comprise a non-polyolefinic polymer in additionto the polyolefin. Favorable examples of the non-polyolefinic polymerinclude the various polymer materials exemplified as the resin filmpossibly forming the substrate, excluding the polyolefins. Thenon-polyolefinic polymer content if any is suitably less than 100 partsby weight to 100 parts by weight of the polyolefin, preferably 50 partsby weight or less, more preferably 30 parts by weight or less, or yetmore preferably 10 parts by weight or less. The non-polyolefinic polymercontent can be 5 parts by weight or less to 100 parts by weight of thepolyolefin, or can be even 1 part by weight or less. The art disclosedherein can be preferably implemented in an embodiment where, forinstance, a polyolefin accounts for 99.5% to 100% by weight of thepolyolefin film

To the substrate, various additive may be added as necessary, such asfillers (inorganic fillers, organic fillers, etc.), anti-aging agent,antioxidant, UV absorber, antistatic agent, lubricant, plasticizer, andcolorant (pigment, dye, etc.). The amount of the various additives addedis usually about 30% by weight or less (e.g. 20% by weight or less,typically 10% by weight or less). For instance, when a pigment (e.g. awhite pigment) is included in the substrate, its content is suitablyabout 0.1% to 10% (e.g. 1% to 8%, typically 1% to 5%) by weight.

The substrate may have a monolayer structure or a multilayer structurein which two or more layers are laminated. For instance, the substratemay have a multilayer (e.g. bilayer) structure in which a polyolefinlayer H comprising HDPE as the primary polymer (a component accountingfor more than 50% of polymers by weight) is laminated with a polyolefinlayer L comprising at least LLDPE or VLDPE as the primary polymer. Thecombined amount of LLDPE and VLDPE in the polyolefin layer L istypically 60% by weight or greater, preferably 75% by weight or greater,or possibly 90% by weight or greater. Usually, from the standpoint ofthe strength and the ease of hand-tearing, the polyolefin layer Hpreferably has a thickness larger than that of the polyolefin layer L. Afavorable example of the polyolefin layer L is a VLDPE layer comprisingVLDPE as the primary polymer (typically a component accounting for morethan 50% by weight, preferably 75% by weight or more, e.g. 90% by weightor more, of the polymer content).

The polyolefin layer L can be the layer (backside layer) forming thesecond face of the substrate. For instance, as shown in FIG. 5, thesubstrate disclosed herein may be a substrate 120 having a multilayerstructure in which a support layer 122 formed of the polyolefin layer Hand a backside layer 124 formed of the polyolefin layer L are laminated.A substrate whose second face is formed of the polyolefin layer L has anadvantage such that a suitable unwinding force is likely to be obtainedeven if the release treatment to the second face is omitted or weakened.An example of the polyolefin layer L favorable to obtain such anadvantage is a VLDPE layer. The thickness of the backside layer can be,for instance, about 1 μm to 200 μm, or it is usually suitably about 2 μmto 100 μm (typically 5 μm to 50 μm). In an embodiment, the thickness ofthe backside layer can be about 2 μm to 20 μm, or even about 3 μm to 15μm (e.g. 5 μm to 10 μm). It should be noted that, even in an embodimentwhere the second face of the substrate is formed of the polyolefin layerL, the polyolefin layer L can be subjected to a suitable surfacetreatment (e.g. release treatment) as necessary. Such an embodiment isalso included in the art disclosed herein.

In the art disclosed herein, the resin film used as the substrate or acomponent thereof can be formed using a biomass material. Here, thebiomass material refers to a reproducible material originating from anorganic resource. Typically, it refers to a material originating from abiological resource (typically a photosynthetic plant) that issustainable and reproducible in the presence of sun light, water andcarbon dioxide. Thus, it excludes a material derived from fossilresources (a fossil-derived material) which would be exhausted upon useafter mined. The biomass material can be, for instance, the reproducibleorganic resource itself or a material obtainable by chemical orbiological synthesis of the organic resource (typically a substanceforming an organism). For instance, the biomass material may be obtainedfrom a plant such as sugarcane and corn. In particular, the biomassmaterial can be ethanol produced from sugarcane or a material obtainablefrom saccharides produced from corn. For instance, as the HDPE describedabove, an HDPE being a biomass material (biomass HDPE) can be used.Similarly, for instance, as the aforementioned LDPE, LLDPE, PP and thelike, the corresponding biomass materials (e.g. biomass LDPE) can beused.

The substrate used in the art disclosed herein may have contours(depressions and/or protrusions) at least on one face. The use of asubstrate having such a contoured surface (e.g. a substrate formedincluding resin film such as polyolefin film) can provide cushioningproperties to the PSA tape or to the PSA tape roll obtained by windingthe PSA tape. The contours can be used to control the tightness ofadhesion between the backside of the substrate and the adhesive face andto adjust the unwinding force or the unwinding force ratio of the PSAtape roll.

The substrate having a contoured surface may be a substrate havingdepressions at least on one face. For instance, it can be a substratehaving the depressions on the second face (the backside, i.e. the faceopposing the adhesive face) thereof. The depressions may be seriallyarranged in a continuous or intermittent straight line at least on oneface (e.g. the second face) of the substrate. In an embodiment, thedepressions can be aligned in a direction intersecting the lengthdirection of the PSA tape. The PSA tape comprising a substrate in suchan embodiment can be easily cut off along the depressions in thesubstrate and easily torn off by hand. From the standpoint of the easeof hand-tearing, the depressions are preferably arranged in a sequencefrom one lengthwise edge to the other lengthwise edge of the substrate.The angle between the length direction of the PSA tape and the directionof the row of the depressions can be, for instance, 90°±60° (i.e. 30° orlarger and 150° or smaller), preferably 90°±45°, more preferably90°±30°, yet more preferably 90°±15°, or even 90°±5°. In a preferableembodiment, the direction of the row of the depressions may be adirection vertically intersecting the length direction of the PSA tape(i.e. a direction with the aforementioned angle being 90°). The PSA tapein such an embodiment exhibits excellent ease of hand-tearing in thewidth direction.

With reference to FIG. 6, a favorable example of the substrate havingcontours on the surface is described. As illustrated, depressions 126are formed on the second face (backside) 120B of substrate 120. Thesedepressions 126 are arranged in a straight row on the surface. Thehorizontal direction (the direction of X-axis) in FIG. 6 corresponds tothe width direction of substrate 120. Depressions 126 are aligned in thewidth direction (i.e. a direction vertically intersecting the lengthdirection) of substrate 120. With respect to the length direction ofsubstrate 120, an arrangement where depressions 126 are aligned in thelength direction can be preferably used. In other words, depressions 126may be arranged in a lattice pattern as a whole, with some of themaligned in the width direction of the substrate and others aligned inthe length direction.

The bottom of a depression in the substrate may have a U-shaped crosssection as shown in FIG. 6, a V-shaped cross section, a rectangular(angular U-shaped) cross section, or a composite or intermediate shapeof these. The internal shape (the shape formed with the inner surface)of the depression can be, for instance, conical or truncated conicalshape tapering toward a bottom such as cone, truncated square pyramid,trigonal pyramid, truncated trigonal pyramid, cone, and truncated cone;columnar shape including cylindrical and a polygonal column (e.g. asquare column, triangular column); spherical shape, dish shape having aflat bottom and a spherical side wall (truncated spherical), or acomposite or intermediate shape of these. In an embodiment, the internalshape of the depression can at least partially include a curved surface.The substrate having depressions in such a shape may be advantageous inview of hand-tearing the PSA tape and obtaining certain strength in thelength direction. In a preferable embodiment of the art disclosedherein, the second face of the substrate has depressions 126 having asquare pyramidal internal shape with curved edges and vertices, with thedepressions 126 crisscrossed in the width and length directions of thesubstrate.

In view of the balance between ease of hand-tearing and strength, thedepth D (the maximum depth, the distance indicated by D in FIG. 6) ofthe depression is preferably selected so that the ratio of D to thethickness S of the substrate, i.e. the ratio D/S, is in a range of 0.2to 0.8 (e.g. 0.2 to 0.5). In particular, the depth D of the depressionis usually suitably about 10 μm to 160 μm (e.g. 20 μm to 100 μm). Inview of the balance between ease of hand-tearing and strength, the width(the distance indicated by W3 in FIG. 6) of the depression is preferablyabout 50 μm to 500 μm (e.g. 70 μm to 400 μm, typically 100 μm to 300μm). In view of the balance between ease of hand-tearing and ease offorming depressions, the space between the depressions (the distanceindicated by L in FIG. 6, it may be the space between two adjacentdepressions) is preferably about 100 μm to 4000 μm (e.g. 300 μm to 3000μm, typically 500 μm to 2000 μm). The depth, width and space of thedepressions can be determined by electron microscopy.

FIG. 6 shows an example in which only the second face 120B of substrate120 has contours, but it is not limited to this. Each of the first andsecond faces 120A and 120B of substrate 120 may have contours, or onlythe first face 120A of substrate 120 may have contours. For instance, inFIG. 6, protrusions (not shown in the drawing) corresponding to thearrangement and shapes of depressions 126 of the second face 120B may beformed on the first face 120A of substrate 120.

In this embodiment, depressions are arranged in a straight row(serially), but are not limited to this arrangement. For instance, thedepressions may be arranged in a row such as a wavy row and a curvedrow. From the standpoint of the ease of hand-tearing, the depressionsare preferably arranged in a straight row.

When depressions are formed on a face of the substrate, the number ofdepressions per unit length (/cm) on the face, counting one for each rowof depressions lined up continuously or intermittently, is 2/cm to 20/cm(e.g. 2/cm to 15/cm, typically 5/cm to 15/cm).

The method for fabricating the substrate with surface contours is notparticularly limited. For instance, it is possible to employ a methodwhere resin film (polyolefin film, etc.) is fabricated by a known orcommonly-used method such as thermoforming (T-die extrusion, inflation)and solution casting; subsequently, onto the resin film in a melted orsoftened state, a sort of a molding roll having a contoured surface ispressed to transfer the shape of the contoured surface onto the resinfilm; a method where onto a pre-molded resin film, a sort of a rollhaving a contoured surface is pressed to transfer the shape of thecontoured surface; and the like. In a favorable example of the methodfor fabricating the substrate, resin film (favorably polyolefin film)extruded from a T-die (T-shaped die) is brought in contact with thesurface of a cooling molding roll (embossing roll) featuring contours onthe surface. For forming contours on the surface of pre-molded resinfilm, it is preferable to use non-stretched resin film in view ofpreventing deformation of the contours formed.

Third Embodiment

In some embodiments of the art disclosed herein, the PSA tape formingthe PSA tape roll may be provided with an anti-rail-drawing portionwhere the adhesiveness of the PSA tape is reduced. The anti-rail-drawingportion is effective when placed on the inner circumferential side inthe vicinity of the winding end edge of the PSA tape. In an embodiment,the anti-rail-drawing portion can be placed in an area from the windingend edge of the PSA tape to one-fourth the circumference (preferablyone-sixth the circumference, more preferably one-eighth thecircumference) inward (towards the roll core). Rail drawing of the PSAtape roll starts at the winding end edge of the PSA tape. By reducingthe adhesiveness of the PSA tape in the vicinity of the winding endedge, the relationship between the adhesive strength to the targetsurface and the adhesive strength to the backside of the PSA tape (whichmay be related to the unwinding force) can be locally adjusted toeffectively prevent rail drawing. When a tear-off location (e.g. cutholes 24 in FIG. 1) is designated in the PSA tape forming the PSA taperoll, the anti-rail-drawing portion can also be placed in an area fromeach tear-off location (i.e. a location where the PSA tape can be tornoff to leave a new winding end edge) to one-fourth the circumferenceinward. The art disclosed herein can effectively prevent loosening ofthe PSA tape even in an embodiment where the anti-rail-drawing portionis provided inward from each tear-off location as described above.

The anti-rail-drawing portion is preferably formed, continuously orintermittently running in a direction (typically in the width direction)intersecting the length direction of the PSA tape. The anti-rail-drawingportion in such a configuration can inhibit degradation of the adhesiveproperties while effectively preventing rail drawing. In an embodiment,the anti-rail-drawing portion can be formed along the inward of thewinding end edge. The anti-rail-drawing portion can be formed in acontinuous or intermittent manner, entirely or partially over the lengthof the winding end edge.

The anti-rail-drawing portion is not limited to a particular embodimentas long as it can locally reduce the adhesive strength of the PSA tape.For instance, in the PSA tape roll in the first embodiment shown in FIG.1, as shown in FIG. 7, an anti-rail-drawing portion can be formed byadhering lead tape 90 to the adhesive face 35 in an area next to thewinding end edge of the PSA tape inward from the edge, wherein the leadtape 90 is formed of a sheet member having a non-adhesive orlow-adhesive surface. In this embodiment, similar lead tape 90 is alsoplaced in contact with each row of cut holes on the innercircumferential side of the roll. Lead tape 90 is not particularlylimited. For instance, various types of resin film, paper, fabric,rubber sheet, foam sheet, metal foil, a composite of these, and the likecan be used. For instance, lead tape 90 can be band-shaped as shown inFIG. 7, but is not limited to this as long as it runs in the widthdirection of the PSA tape.

Placing such lead tape 90 can prevent rail drawing and also prevent thePSA tape from splitting in the length direction from the winding endedge when the adhesive face is renewed. In other words, when hair, lintand the like are stuck across the outer circumferential edge of the PSAtape roll, in a process of peeling the outer circumferential edge of thePSA tape from the PSA tape roll, the PSA tape may split in the lengthdirection from the winding end edge due to the stuck hair, lint and thelike. By placing lead tape 90 inward from the winding end edge of thePSA tape (and also inward from locations where the PSA tape can be tornoff to leave new winding end edges), the winding end edge can bereinforced with the lead tape 90. This makes it easier to peel the PSAtape from the PSA tape roll with the stuck hair, lint and the like,thereby facilitating renewal of the adhesive face. From such astandpoint, in an embodiment, lead tape 90 with higher strength (tensilestrength, tear strength, etc.) than that of substrate 21 can bepreferably used. For instance, lead tape 90 formed of resin film such asPET and PP can be used. The resin film forming lead tape 90 may comprisean antistatic agent to make it less susceptible to dust accumulation. Inan embodiment, as the lead tape 90, a material colored with a differentcolor from that of substrate 20 can be preferably used. This makes iteasier to locate the outer winding end edge or cut holes 24 in PSA tape12.

In the art disclosed herein, the method for forming theanti-rail-drawing portion is not limited to a method where anon-adhesive or low-adhesive member such as the lead tape describedabove is placed on the adhesive face. For instance, theanti-rail-drawing portion can be formed by deposition of non-adhesive orlow-adhesive particles on a prescribed location in the adhesive face.Such particles can be supplied to the adhesive face as a compositionobtained by dispersing or dissolving the particles in a suitable medium.For instance, by supplying a colored or colorless pigment-containingcomposition, possibly a composition considered as ink or paint, to anarea inward from the winding end edge and an area inward from each rowof cut holes (typically in the width direction of the PSA tape), theadhesive strength of the adhesive face in this area can be reduced orminimized to form an anti-rail-drawing portion. The composition can besupplied to the area, for instance, by applying or printing (e.g. inkjetprinting, etc.) the composition by a known method. The composition canbe supplied after the first and second layers are formed. Alternatively,the composition can be supplied, for instance, after the first layer isformed, but before the second layer is formed. In this case, theadhesive strength of the first layer is also reduced or minimized toreduce the adhesive strength of the adhesive face as a whole, whereby aneffect to prevent rail drawing can be obtained.

In the art disclosed herein, the anti-rail-drawing portion may be asection where the first layer is not placed on the first face of thesubstrate in a prescribed region (in a band-shaped range running in thewidth direction of the PSA tape) inward from the winding end edge of thePSA tape or inward from each row of cut holes. The anti-rail-drawingportion in such an embodiment can be formed, for instance, byintermittently applying the PSA for forming the first layer in thelength direction of the substrate. Alternatively, the anti-rail-drawingportion can be formed as follows: masking tape is adhered to an area ofthe first face of the substrate where an anti-rail-drawing portion is tobe formed; over the masking tape, the first layer-forming PSA iscontinuously applied; subsequently, the masking tape is peeled off (i.e.the first layer formed on the masking tape is removed along with themasking tape).

The width of the anti-rail-drawing portion can be, for instance, 1 mm orgreater. It is usually suitably 2 mm or greater (e.g. 3 mm or greater).With increasing width of the anti-rail-drawing portion, theanti-rail-drawing properties tend to be enhanced. The width of theanti-rail-drawing portion can be, for instance, 50 mm or less. From thestandpoint of retaining the adhesive properties and preventingroll-loosening, the width of the anti-rail-drawing portion is usuallysuitably 30 mm or less, or preferably 15 mm or less (e.g. 10 mm orless). The anti-rail-drawing portion can be provided to an area outward(towards the winding end edge) from a tear-off location, in addition tothe area inward from the tear-off location. For instance, theanti-rail-drawing portion can be provided across (to both sides of) atear-off location and along the tear-off location.

Fourth Embodiment

The art disclosed herein can be favorably implemented in an embodimentusing a substrate comprising a foam sheet in the PSA tape roll. With theuse of a foam sheet as the substrate or a component thereof, goodcushioning properties can be provided to the PSA tape and to the PSAtape roll obtained by winding the PSA tape. Specific examples of thematerial forming the foam sheet include polyolefinic resin foam such asPE foam and PP foam; polyester-based resin foam such as PET foam,polyethylene naphthalate foam, and polybutylene terephthalate foam;polyvinyl chloride-based resin foam such as polyvinyl chloride foam;vinyl acetate-based resin foam; polyphenylene sulfide resin foam;amide-based resin foam such as polyamide (nylon) resin foam and whollyaromatic polyamide (aramid) resin foam; polyimide-based resin foam;polyether ether ketone (PEEK) foam; styrene-based resin foam such aspolystyrene foam; and urethane-based resin foam such as polyurethaneresin foam. As the foam, rubber-based resin foam such as polychloroprenerubber foam can be used as well. As the foam, closed-cell foam ispreferable.

Examples of preferable foam include polyolefinic resin foam. As theplastic material forming the polyolefinic foam (i.e. as the polyolefinicresin), various known or commonly-used polyolefinic resins can be usedwithout particular limitations. Examples include PE such as low densityPE (LDPE), linear low density PE (LLDPE), high density PE (HDPE), andmetallocene catalyst-based linear low density PE; PP; ethylene-propylenecopolymers; and ethylene-vinyl acetate copolymers. These polyolefinicresins can be used singly as one species or in a combination of two ormore species. In particular, a preferable PE-based foam sheet isessentially formed of PE-based resin foam. Here, the PE-based resinrefers to a resin whose primary monomer (i.e. the primary componentamong monomers) is ethylene, possibly including HDPE, LDPE and LLDPE aswell as an ethylene-propylene copolymer and an ethylene-vinyl acetatecopolymer with more than 50% ethylene by weight (copolymerizationratio).

The density (apparent density) of the foam sheet is not particularlylimited. It is usually preferably 10 kg/m³ to 200 kg/m³, or morepreferably 10 kg/m³ to 100 kg/m³ (typically 15 kg/m³ to 50 kg/m³). Whenthe density is at or above the prescribed value, the strength of thefoam sheet (and further of the PSA tape) as well as the handlingproperties tend to increase. On the other hand, when the density is ator below the prescribed value, the cushioning properties as well as thesolid dirt-collecting ability and holding (anti-falling) properties ofthe same tend to increase. The density (apparent density) of the foamsheet can be determined by a method based on JIS K 6767:1999.

The tensile strength of the foam sheet (e.g. a polyolefinic foam sheet)is not particularly limited. For instance, the tensile strength in thelength direction (MD) is preferably 0.25 MPa to 2.5 MPa (more preferably0.3 MPa to 2.0 MPa, typically 0.5 MPa to 1.5 MPa). The tensile strengthin the width direction (TD) is preferably 0.1 MPa to 1.8 MPa (morepreferably 0.15 MPa to 1.2 MPa, typically 0.2 MPa to 0.6 MPa). When thetensile strength is in these ranges, the strength of the PSA tapeincreases, whereby greater handling properties can be obtained. Thetensile strength of the foam sheet is determined based on JIS K6767:1999.

The elongation of the foam sheet (e.g. a polyolefinic foam sheet) is notparticularly limited. For instance, the MD elongation is preferably 20%to 400% (more preferably 20% to 300%, typically 25% to 100%). The TDelongation is preferably 15% to 300% (more preferably 20% to 200%,typically 25% to 100%) An elongation in these ranges tends to bringabout greater solid dirt-collecting ability and strength of the PSAtape. The elongation of the foam sheet is determined based on JIS K6767:1999.

The tear strength of the foam sheet (e.g. a polyolefinic foam sheet) isnot particularly limited. For instance, the MD tear strength ispreferably 15 N/m to 120 N/m (more preferably 15 N/m to 80 N/m,typically 20 N/m to 50 N/m). The TD tear strength is preferably 6 N/m to100 N/m (more preferably 8 N/m to 60 N/m, typically 10 N/m to 30 N/m).The tear strength in these ranges tends to bring about, for instance,greater handling properties for renewing the outer surface of the stickycleaner, etc., along with greater strength. The tear strength of thefoam sheet is determined based on JIS K 6767:1999.

The permanent compression set of the foam sheet (e.g. a polyolefinicfoam sheet) is not particularly limited. As the support substrate, it ispreferable to use a foam sheet that exhibits a permanent compression setof, for instance, about 3.0% to 15.0% (more preferably 5.0% to 15.0%,typically 6.0% to 12.0%). A permanent compression set in these rangestends to further enhance the solid dirt-collecting ability and thestrength of the PSA tape. The permanent compression set of the foamsheet is determined based on JIS K 6767:1999.

On the second face (backside) of the substrate, an approximately 1 μm to500 μm (e.g. 5 μm to 300 μm, typically 10 μm to 200 μm) thick releaselayer formed from a non-polar resin and the like is preferably formed.As the non-polar resin, a polyolefin such as polyethylene (e.g. VLDPE,LLDPE) can be preferably used. In addition to or in place of the releaselayer, a surface treatment (a release treatment to prevent an excessiveincrease in unwinding force) such as coating of a silicone-based releaseagent and the like can be provided.

With respect to other features besides the substrate material, the PSAtape roll with a substrate using such a foam sheet can be constituted inthe same manner as the PSA tape rolls according to the respectiveembodiments described earlier. The art disclosed herein can beimplemented, for instance, in an embodiment where a polyolefinic foamsheet is used as the substrate of the PSA tape roll 10 in the firstembodiment.

The matters disclosed herein include the following:

(1) A sticky cleaner comprising a PSA tape having an adhesive face on afirst face of a substrate, wherein

the PSA tape constitutes a PSA tape roll wound with the adhesive face onthe outside,

on the first face of the substrate, the PSA tape has a first layerformed of a PSA and a second layer formed of a viscoelastic material,

the adhesive face comprises a first section where the first layer isexposed and a second section where the second layer is exposed,

the second section protrudes further out of the PSA tape roll, relativeto the first section, and

the PSA tape roll exhibits an unwinding force F₀ at 0° C. and anunwinding force F₃₀ at 30° C., F₀ being up to 10 times F₃₀.

(2) The sticky cleaner according to (1) above wherein the viscoelasticmaterial forming the second layer is an acrylic viscoelastic material.

(3) The sticky cleaner according to (1) or (2) above wherein theviscoelastic material forming the second layer is an acrylic PSA.

(4) The sticky cleaner according to any of (1) to (3) above wherein aplurality of the second sections are formed, separated by spaces in thewidth direction.

(5) The sticky cleaner according to any of (1) to (4) wherein the secondsection is formed in a line running in the length direction of the PSAtape.

(6) The sticky cleaner according to any of (1) to (5) above wherein thesecond layer is formed in lines running in the length direction of thePSA tape, separated by spaces in the width direction of the PSA tape.

(7) The sticky cleaner according to any of (1) to (6) above wherein thesecond layer is partially formed over the first layer.

(8) The sticky cleaner according to any of (1) to (6) above wherein thesecond layer is directly formed on the first face of the substrate.

(9) The sticky cleaner according to any of (1) to (8) above wherein thesecond layer is larger in thickness than the first layer.

(10) The sticky cleaner according to any of (1) to (9) above wherein thesubstrate is selected from laminates comprising one, two or more amongpaper, resin film and a foam sheet.

(11) The sticky cleaner according to any of (1) to (10) above whereindepressions are formed in the second face of the substrate, with thedepressions serially arranged in a continuous or intermittent straightline intersecting the length direction of the PSA tape.

(12) The sticky cleaner according to any of (1) to (11) above whereinthe second layer comprises an acrylic block copolymer as the basepolymer.

(13) The sticky cleaner according to (12) above wherein the acrylicblock copolymer comprises a soft segment and a hard segment, with thesoft segment comprising a monomer unit derived from n-butyl acrylate.

(14) The sticky cleaner according to (13) above wherein the soft segmentcomprises a monomer unit derived from n-butyl acrylate and a monomerunit derived from 2-ethylhexyl acrylate.

(15) The sticky cleaner according to any of (1) to (14) above whereinthe second layer comprises a filler.

(16) The sticky cleaner according to (15) above wherein the filleraccounts for about 10% or higher and about 50% or lower by weight of thesecond layer.

(17) The sticky cleaner according to any of (1) to (16) above whereinthe second layer has a cross-sectional area A (mm²) in the widthdirection of the PSA tape and a percent (%) weight R of the elastomercontent in the second layer, having a product (an AR value) equal to orless than 2.5.

(18) The sticky cleaner according to (17) above wherein the AR value isabout 0.5 or greater and about 2.3 or less.

(19) The sticky cleaner according to any of (1) to (18) above whereinthe second layer has a cross-sectional area of 0.005 mm² or greater and0.1 mm² or less in a cross section in the width direction of the PSAtape.

(20) The sticky cleaner according to any of (1) to (19) above whereinthe first layer is a rubber-based PSA layer.

(21) The sticky cleaner according to any of (1) to (20) above whereinthe PSA tape has cut holes running in a direction intersecting thelength direction of the PSA tape.

(22) The sticky cleaner according to any of (1) to (21) above whereinthe PSA tape has an anti-rail-drawing portion where the adhesiveness ofthe PSA tape is reduced, in an area up to one-fourth the circumferenceinward from the winding end edge of the PSA tape.

(23) The sticky cleaner according to (22) above wherein theanti-rail-drawing portion is formed of a sheet member placed on theadhesive face, with the sheet member having a non-adhesive orlow-adhesive outer face.

(24) The sticky cleaner according to (22) above wherein theanti-rail-drawing portion is formed by depositing non-adhesive orlow-adhesive particles onto the adhesive face.

(25) A sticky cleaner comprising a PSA tape roll in which a PSA tapehaving an adhesive face on a first face of a substrate is wound with theadhesive face on the outside, wherein

the PSA tape comprises, on the first face of the substrate, a firstlayer formed of a PSA and a second layer formed of a viscoelasticmaterial,

the second layer is formed in lines running in the length direction ofthe PSA tape, and

the second layer has a cross-sectional area A (mm²) in a cross sectionin the width direction of the PSA tape and a percent (%) weight R of theelastomer content in the second layer, having a product (an AR value)equal to or less than 2.5.

EXAMPLES

Several worked examples relating to the present invention are describedbelow, but the present invention is not intended to be limited to theseexamples. In the description below, “parts” and “%” are based on weightunless otherwise specified.

<Fabrication of PSA Tape Rolls>

Example 1

As described below, was fabricated a PSA tape roll having a first layerformed of a rubber-based PSA and a second layer formed of an acrylicviscoelastic material on a first face of a substrate.

As the rubber-based PSA for forming the first layer, was used SIS-basedPSA formed from 100 parts of SIS as the base polymer, 130 parts oftackifier resin and 100 parts of process oil. As the SIS, was used tradename QUINTAC 3520 available from Zeon Corporation. As the tackifierresin, was used trade name T-REZ RC093 available from Tonen GeneralSekiyu K. K. As the process oil, was used trade name DIANA PROCESS OILNS90S available from Idemitsu Kosan Co., Ltd.

Were kneaded 100 parts of acrylic polymer as the base polymer, 160 partsof filler master batch, 50 parts of acrylic oligomer and 2.4 parts ofblue pigment to prepare the acrylic viscoelastic material (PSA) forforming the second layer. As the acrylic polymer, was used an acrylicblock copolymer synthesized by a known living anionic polymerizationmethod. This acrylic block copolymer has a tri-block structure ofpolyMMA block-poly2EHA/BA block-polyMMA block (or MMA-2EHA/BA-MMAhereinafter). The 2EHA to BA ratio (copolymerization ratio) by weight inthe poly2EHA/BA block was approximately 50/50. The polyMMA block (twopolyMMA blocks combined) to poly2EHA/BA block ratio (MMA/(2EHA+BA)) byweight was about 18/82. The acrylic polymer A had a Mw of 10×10⁴ and aMn of 8.4×10⁴ with Mw/Mn being 1.21. The filler master batch usedcontained calcium carbonate particles (filler) and polyethylene resin ata weight ratio of 8:2. As the acrylic oligomer, was used trade nameALFON UP-1000 (functional group-free acrylic oligomer with Mw of about3000) available from Toagosei Co., Ltd. The percent (%) weight R of theelastomer content in the acrylic viscoelastic material was 58%.

Using a double-screw extruder equipped with an extrusion die, therubber-based PSA and the acrylic viscoelastic material were heated,melted, and extruded from the die, applied to a first face of asubstrate to fabricate a PSA tape having a similar cross-sectionalstructure to PSA tape 12 shown in FIG. 2. As substrate 20, was used asubstrate obtained by laminating pure white paper (40 g grammage, 50 μmthick, 160 mm wide) with 20 μm thick polyethylene film on the secondface (opposite from the face where the adhesive face was formed, i.e.the backside). A 150 mm wide band of the first layer 31 was formed in acentral area of the width of substrate 20. The thickness T1 of the firstlayer 31 was 15 μm. Over the first layer 31, were formed 73 straightlines of the second layer 32 running in the length direction of PSA tape12 spaced apart by an approximately constant pitch P (about 2 mm here).Each line of the second layer 32 had a width W2 of 0.37 mm. By this, onthe first face 20A of substrate 20, was formed a 150 mm wide adhesiveface 35 comprising first sections 31A as parts of the first layer 31 notcovered with the second layer 32 and second sections 32A where the PSAlayer 32 was exposed. On the adhesive face 35, the protruding height T2of the second sections 32A relative to the first sections 31A was 70 μm.

The PSA tape in the embodiment above was wound with the adhesive face onthe outside to obtain a PSA tape roll according to this Example.

Example 2

In place of the acrylic viscoelastic material for forming the secondlayer in Example 1, was used CEBC-based viscoelastic material (PSA)formed from 100 parts of CEBC as the base polymer, 50 parts of tackifierresin, 100 parts of process oil and 2.4 parts of blue pigment. As theCEBC, was used trade name DYNARON 6200P available from JSR Corporation.As the tackifier resin, was used trade name CLEARON P-105 available fromYasuhara Chemical Co., Ltd. As the process oil, was used trade nameDIANA PROCESS OIL PW-90 available from Idemitsu Kosan Co., Ltd.Otherwise in the same manner as Example 1, was obtained a PSA tape rollaccording to this Example. The percent (%) weight R of the elastomercontent in the CEBC-based viscoelastic material was 99%.

<Measurements and Evaluations>

(Determination of Unwinding Force)

With respect to the PSA tape roll of each Example, the unwinding forcewas determined at 0° C., 20° C. and 30° C. Five measurements (n=5) weretaken at each measurement temperature. From the unwinding forces F₀ at0° C. and F₃₀ at 30° C., the unwinding force ratio (F₀/F₃₀) wasdetermined. The results are shown in Table 1.

(Unwinding Workability)

The PSA tape roll according to each Example was stored in an environmentat 0° C. for at least one hour. Subsequently, a tester held the outerterminal of the PSA tape (the winding end edge) by hand and withdrew itin the tangential direction at a rate of about 1000 mm/min. For eachExample, the test (withdrawal) was carried out five times. Based on howthis operation worked out, the unwinding workability was graded on thefollowing two-grade scale:

E: No tearing or splitting of PSA tape occurred (excellent unwindingworkability)

P: Tearing or splitting occurred at least once (poor unwindingworkability)

(Anti-Roll-Loosening Properties)

The PSA tape roll according to each Example was kept standing on ahorizontal test board with the winding axis in the vertical directionand stored at 23° C. and 50% RH for two hours. Subsequently, withrespect to the top side of the PSA tape roll standing on the test board,was visually inspected whether or not peeling (lifting) of the windingend edge of the PSA tape from the inner part of the PSA tape roll hadoccurred. Anti-roll-loosening properties were evaluated on the followingtwo-grade scale:

E: No peeling of PSA tape observed or the length of the peeled part ofPSA tape was 1 cm or less from the winding end edge (excellentanti-roll-loosening properties)

P: Peeling of PSA tape occurred over a length of 5 cm or greater fromthe winding end edge (poor anti-roll-loosening properties)

The test results are shown in Table 1.

TABLE 1 Unwinding force Unwinding Anti-roll- (N/150 mm) force ratioUnwinding loosening 0° C. 20° C. 30° C. (F₀/F₃₀) workability propertiesEx. 1 2.3 1.9 0.8 2.9 E E Ex. 2 7.1 0.5 0.2 35.5 P P

As shown in Table 1, the PSA tape roll of Example 1 whose unwindingforce exhibited low dependence on temperature was easy to unwind even ata low temperature while showing great anti-roll-loosening properties atroom temperature.

(Determination of Rotational Resistance)

The rotational resistance of the PSA tape roll according to each Examplewas determined with respect to three different target surfaces, namely,a carpet (an acrylic carpet available from Sun Holiday, trade name HD1,pile length 6 mm (loop)), a waxed flooring material (Daiken Corporation,MIRAGE F-series), and a wax-free flooring material (Daiken Corporation,LVAT-MW).

In particular, to a rolling member 52 of a jig 50 having a shapeoutlined in FIGS. 3 and 4, was attached PSA tape roll 10 after storedunder the conditions described above. In a measurement environment at23° C. and 50% RH, grip 54 of jig 50 was lightly held by a tester androlled over a surface 56 to be cleaned at a rate of about 30 m/min at anangle θ of 55° (0=angle between the shaft of jig 50 and surface 56 beingcleaned). During this, the force exerted on grip 54 (i.e. the rotationalresistance) was determined with a digital force gauge.

TABLE 2 Rotational resistance (N/150 mm) Flooring Flooring Carpet(waxed) (not waxed) Ex. 1 7.3 5.0 7.9 Ex. 2 9.7 6.6 16.6

As shown in Table 2, the sticky cleaner using the PSA tape rollaccording to Example 1 operated smoothly on all target surfaces withadequate operational feelings. As compared to Example 2, the PSA taperoll according to Example 1 varied little in rotational resistance inrelation to the types of target surface and was suitable for use on awax-free flooring surface as well.

(Tensile Test)

With respect to the viscoelastic material used for forming the secondlayer in each Example, its breaking strength and the elongation at breakwere determined. Each viscoelastic material in a hot melt state wasallowed to cool on a release liner to form a 1 mm thick sheet. This wasdie-cut to prepare a test piece for the measurement. The results areshown in Table 3.

(Anti-Stringiness Properties)

With respect to the PSA tape according to each Example, while the PSAtape was torn off, the degree of stringiness of the second layer wasevaluated. In particular, for the PSA tape according to each Example, atone end of the width direction (at one lengthwise end), a cut of about 2cm in length running in the width direction was made with scissors. ThePSA tape was hand-held at both sides of the cut and pulled apartapproximately in the length direction (in the running direction of thesecond layer) to tear a piece of the PSA tape off the rest. During this,with respect to the second layer, whether or not sticky strings formedwas visually inspected. When significant sticky string formation wasobserved, the anti-stringiness was graded “P” (poor anti-stringiness);when no notable sticky string formation was observed, it was graded “E”(excellent anti-stringiness). The results are shown in Table 3. Table 3also shows the cross-sectional area A of the second layer and thepercent weight R of the elastomer content in the viscoelastic materialforming the second layer.

TABLE 3 Elongation Breaking Cross-sec- % weight Anti- at break strengthtional area R of AR stringi- (%) (N/10 mm) A (mm²) elastomer value nessEx. 1 298 5.3 0.0259 58 1.50 E Ex. 2 2998 12.3 0.0259 99 2.56 P

As shown in Table 3, with respect to the PSA tape of Example 1 with alow AR value, the anti-stringiness was clearly superior to that of thePSA tape of Example 2.

Although specific embodiments of the present invention have beendescribed in detail above, these are merely for illustrations and do notlimit the scope of the claims. The art according to the claims includesvarious modifications and changes made to the specific embodimentsillustrated above.

REFERENCE SIGNS LIST

-   1 sticky cleaner-   10, 110 PSA tape roll-   12, 112 PSA tape-   14 roll core-   20, 120 substrate-   20A, 120A first faces-   20B, 120B second faces-   22, 23 non-adhesive areas (dry edges)-   24 cut hole-   31, 131 first layers-   31A, 131A first sections-   32, 132 second layers-   32A, 132A second sections-   35, 135 adhesive faces-   50 jig-   90 lead tape-   126 depression

1. A sticky cleaner comprising a pressure-sensitive adhesive tape havingan adhesive face on a first face of a substrate, wherein thepressure-sensitive adhesive tape constitutes a pressure-sensitiveadhesive tape roll wound with the adhesive face on the outside, on thefirst face of the substrate, the pressure-sensitive adhesive tape has afirst layer formed of a pressure-sensitive adhesive and a second layerformed of a viscoelastic material, the first and second layers areformed directly on the first face of the substrate, the first layer is arubber-based pressure-sensitive adhesive layer, the viscoelasticmaterial forming the second layer is an acrylic viscoelastic materialcomprising an acrylic block copolymer as its base polymer, the adhesiveface comprises a first section where the first layer is exposed and asecond section where the second layer is exposed, the second sectionprotrudes further out of the pressure-sensitive adhesive tape roll,relative to the first section, the acrylic block copolymer isessentially free of monomer units other than alkyl(meth)acrylate units,the second layer has a cross-sectional area A (mm²) in the widthdirection of the pressure-sensitive adhesive tape and a percent (%)weight R of the elastomer content in the second layer, where a productof the numerical value A and the numerical value R equals to or is lessthan 2.5, the pressure-sensitive adhesive tape roll exhibits anunwinding force F₀ at 0° C. and an unwinding force F₃₀ at 30° C., F₀being 1 times or more and up to 10 times F₃₀, and the unwinding forceF₃₀ is 0.3 N/150 mm or greater.
 2. The sticky cleaner according to claim1 wherein the acrylic block copolymer comprises a soft segment and ahard segment, with the soft segment comprising a monomer unit derivedfrom n-butyl acrylate.
 3. The sticky cleaner according to claim 1wherein the second layer comprises a filler.
 4. The sticky cleaneraccording to claim 3, wherein the filler comprises a pigment.
 5. Thesticky cleaner according to claim 1 wherein a plurality of the secondsections are formed, separated by spaces in the width direction.
 6. Thesticky cleaner according to claim 1 wherein the second section is formedin a line running in the length direction of the pressure-sensitiveadhesive tape.
 7. The sticky cleaner according to claim 1 wherein linesof the second layer are placed, running in the length direction of thepressure-sensitive adhesive tape, separated by spaces in the widthdirection of the pressure-sensitive adhesive tape.
 8. A sticky cleanercomprising a pressure-sensitive adhesive tape having an adhesive face ona first face of a substrate, wherein the pressure-sensitive adhesivetape constitutes a pressure-sensitive adhesive tape roll wound with theadhesive face on the outside, on the first face of the substrate, thepressure-sensitive adhesive tape has a first layer formed of apressure-sensitive adhesive and a second layer formed of a viscoelasticmaterial, the first and second layers are formed directly on the firstface of the substrate, the first layer is a rubber-basedpressure-sensitive adhesive layer, the viscoelastic material forming thesecond layer is an acrylic viscoelastic material comprising an acrylicblock copolymer as its base polymer, the adhesive face comprises a firstsection where the first layer is exposed and a second section where thesecond layer is exposed, the second section protrudes further out of thepressure-sensitive adhesive tape roll, relative to the first section, aplurality of the second layers are formed in lines running in the lengthdirection of the pressure-sensitive adhesive tape, separated by spacesin the width direction of the pressure sensitive adhesive tape, each ofthe lines has a width W2 of 0.1 mm or greater and 0.7 mm or less and hasa thickness T2 of 50 μm or greater and 100 μm or less, the second layerhas a cross-sectional area A (mm²) in the width direction of thepressure-sensitive adhesive tape and a percent (%) weight R of theelastomer content in the second layer, where a product of the numericalvalue A and the numerical value R equals to or is less than 2.5, thepressure-sensitive adhesive tape roll exhibits an unwinding force F₀ at0° C. and an unwinding force F₃₀ at 30° C., F₀ being 1 times or more andup to 10 times F₃₀, and the unwinding force F₃₀ is 0.3 N/150 mm orgreater.
 9. The sticky cleaner according to claim 8 wherein the acrylicblock copolymer comprises a soft segment and a hard segment, with thesoft segment comprising a monomer unit derived from n-butyl acrylate.10. The sticky cleaner according to claim 8 wherein the second layercomprises a filler.
 11. The sticky cleaner according to claim 10,wherein the filler comprises a pigment.
 12. The sticky cleaner accordingto claim 8 having cut holes running in a direction intersecting thelength direction of the pressure-sensitive adhesive tape.
 13. The stickycleaner according to claim 8 having an area up to one fourth itscircumference inward from the winding end edge of the pressure-sensitiveadhesive tape, with the area provided with an anti-rail-drawing portionwhere the pressure-sensitive adhesive tape exhibit reduced adhesiveness.14. The sticky cleaner according to claim 8, wherein the second layercomprises an oligomer selected from the group consisting of acrylicoligomers and acrylic urethane-based oligomers.
 15. The sticky cleaneraccording to claim 14, wherein an amount of the oligomer is 10 parts byweight or greater and 80 parts by weight or less based on 100 parts byweight of the base polymer.
 16. The sticky cleaner according to claim14, wherein the oligomer has a weight average molecular weight (Mw) of800 or greater and 30000 or less.
 17. The sticky cleaner according toclaim 8, wherein the second layer is essentially free of a plasticizer.18. The sticky cleaner according to claim 10, wherein a percent weightof the filler in the second layer is 3% or higher and 60% or lower.